staging: rtlwifi: Fix potential NULL pointer dereference of kzalloc

phydm.internal is allocated using kzalloc which is used multiple
times without a check for NULL pointer. This patch avoids such a
scenario by returning 0, consistent with the failure case.
Signed-off-by: Aditya Pakki <pakki001@umn.edu>
Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtlwifi/phydm/rtl_phydm.c

@@ -180,6 +180,8 @@ static int rtl_phydm_init_priv(struct rtl_priv *rtlpriv,
 
 	rtlpriv->phydm.internal =
 		kzalloc(sizeof(struct phy_dm_struct), GFP_KERNEL);
+	if (!rtlpriv->phydm.internal)
+		return 0;
 
 	_rtl_phydm_init_com_info(rtlpriv, ic, params);