staging: rtl8712: rtl8712_cmd.c: fixed comparison to null

This patch fixes multiple "comparison to NULL"
checkpatch.pl issues:

CHECK: Comparison to NULL could be written "!pcmd"
+               if (pcmd == NULL)
Signed-off-by: Juliana Rodrigues <juliana.orod@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8712/rtl8712_cmd.c

@@ -135,7 +135,7 @@ static u8 read_macreg_hdl(struct _adapter *padapter, u8 *pbuf)
 
 	/*  invoke cmd->callback function */
 	pcmd_callback = cmd_callback[pcmd->cmdcode].callback;
-	if (pcmd_callback == NULL)
+	if (!pcmd_callback)
 		r8712_free_cmd_obj(pcmd);
 	else
 		pcmd_callback(padapter, pcmd);
@@ -149,7 +149,7 @@ static u8 write_macreg_hdl(struct _adapter *padapter, u8 *pbuf)
 
 	/*  invoke cmd->callback function */
 	pcmd_callback = cmd_callback[pcmd->cmdcode].callback;
-	if (pcmd_callback == NULL)
+	if (!pcmd_callback)
 		r8712_free_cmd_obj(pcmd);
 	else
 		pcmd_callback(padapter, pcmd);
@@ -165,7 +165,7 @@ static u8 read_bbreg_hdl(struct _adapter *padapter, u8 *pbuf)
 	if (pcmd->rsp && pcmd->rspsz > 0)
 		memcpy(pcmd->rsp, (u8 *)&val, pcmd->rspsz);
 	pcmd_callback = cmd_callback[pcmd->cmdcode].callback;
-	if (pcmd_callback == NULL)
+	if (!pcmd_callback)
 		r8712_free_cmd_obj(pcmd);
 	else
 		pcmd_callback(padapter, pcmd);
@@ -178,7 +178,7 @@ static u8 write_bbreg_hdl(struct _adapter *padapter, u8 *pbuf)
 	struct cmd_obj *pcmd  = (struct cmd_obj *)pbuf;
 
 	pcmd_callback = cmd_callback[pcmd->cmdcode].callback;
-	if (pcmd_callback == NULL)
+	if (!pcmd_callback)
 		r8712_free_cmd_obj(pcmd);
 	else
 		pcmd_callback(padapter, pcmd);
@@ -194,7 +194,7 @@ static u8 read_rfreg_hdl(struct _adapter *padapter, u8 *pbuf)
 	if (pcmd->rsp && pcmd->rspsz > 0)
 		memcpy(pcmd->rsp, (u8 *)&val, pcmd->rspsz);
 	pcmd_callback = cmd_callback[pcmd->cmdcode].callback;
-	if (pcmd_callback == NULL)
+	if (!pcmd_callback)
 		r8712_free_cmd_obj(pcmd);
 	else
 		pcmd_callback(padapter, pcmd);
@@ -207,7 +207,7 @@ static u8 write_rfreg_hdl(struct _adapter *padapter, u8 *pbuf)
 	struct cmd_obj *pcmd  = (struct cmd_obj *)pbuf;
 
 	pcmd_callback = cmd_callback[pcmd->cmdcode].callback;
-	if (pcmd_callback == NULL)
+	if (!pcmd_callback)
 		r8712_free_cmd_obj(pcmd);
 	else
 		pcmd_callback(padapter, pcmd);
@@ -227,7 +227,7 @@ static struct cmd_obj *cmd_hdl_filter(struct _adapter *padapter,
 {
 	struct cmd_obj *pcmd_r;
 
-	if (pcmd == NULL)
+	if (!pcmd)
 		return pcmd;
 	pcmd_r = NULL;
 
@@ -416,7 +416,7 @@ int r8712_cmd_thread(void *context)
 	/* free all cmd_obj resources */
 	do {
 		pcmd = r8712_dequeue_cmd(&(pcmdpriv->cmd_queue));
-		if (pcmd == NULL)
+		if (!pcmd)
 			break;
 		r8712_free_cmd_obj(pcmd);
 	} while (1);
@@ -431,7 +431,7 @@ void r8712_event_handle(struct _adapter *padapter, uint *peventbuf)
 	void (*event_callback)(struct _adapter *dev, u8 *pbuf);
 	struct	evt_priv *pevt_priv = &(padapter->evtpriv);
 
-	if (peventbuf == NULL)
+	if (!peventbuf)
 		goto _abort_event_;
 	evt_sz = (u16)(le32_to_cpu(*peventbuf) & 0xffff);
 	evt_seq = (u8)((le32_to_cpu(*peventbuf) >> 24) & 0x7f);