staging: rtl8723bs: Remove set but not used variable 'oldcnt'

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/staging/rtl8723bs/hal/sdio_ops.c: In function sdio_read_port:
drivers/staging/rtl8723bs/hal/sdio_ops.c:430:6: warning: variable oldcnt set but not used [-Wunused-but-set-variable]

It is not used since commit dedf215b ("staging:
rtl8723bs: remove unused code")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: zhengbin <zhengbin13@huawei.com>
Link: https://lore.kernel.org/r/1570354382-86879-1-git-send-email-zhengbin13@huawei.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8723bs/hal/sdio_ops.c

@@ -427,7 +427,6 @@ static u32 sdio_read_port(
 	struct adapter *adapter;
 	struct sdio_data *psdio;
 	struct hal_com_data *hal;
-	u32 oldcnt;
 	s32 err;
 
 
@@ -437,7 +436,6 @@ static u32 sdio_read_port(
 
 	HalSdioGetCmdAddr8723BSdio(adapter, addr, hal->SdioRxFIFOCnt++, &addr);
 
-	oldcnt = cnt;
 	if (cnt > psdio->block_transfer_len)
 		cnt = _RND(cnt, psdio->block_transfer_len);
 /* 	cnt = sdio_align_size(cnt); */