staging: rtl8723bs: fix warning comparison to NULL

This patch fixes below issue reported by checkpatch

CHECK: Comparison to NULL could be written "!pxmitbuf->pallocated_buf"
+               if (pxmitbuf->pallocated_buf == NULL)
Signed-off-by: Hariprasad Kelam <hariprasad.kelam@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8723bs/os_dep/xmit_linux.c

@@ -50,7 +50,7 @@ int rtw_os_xmit_resource_alloc(struct adapter *padapter, struct xmit_buf *pxmitb
 {
 	if (alloc_sz > 0) {
 		pxmitbuf->pallocated_buf = rtw_zmalloc(alloc_sz);
-		if (pxmitbuf->pallocated_buf == NULL)
+		if (!pxmitbuf->pallocated_buf)
 			return _FAIL;
 
 		pxmitbuf->pbuf = (u8 *)N_BYTE_ALIGMENT((SIZE_PTR)(pxmitbuf->pallocated_buf), XMITBUF_ALIGN_SZ);