staging: rtl8712: Remove NULL comparison

Remove NULL comparison by using '!' operator. Problem found
using checkpatch.pl
CHECK: Comparison to NULL could be written "!ptmpchar"
Signed-off-by: Amitoj Kaur Chawla <amitoj1606@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8712/hal_init.c

@@ -178,7 +178,7 @@ static u8 rtl8712_dl_fw(struct _adapter *padapter)
 			  fwhdr.img_IMEM_size : fwhdr.img_SRAM_size;
 		maxlen += txdscp_sz;
 		ptmpchar = kmalloc(maxlen + FWBUFF_ALIGN_SZ, GFP_ATOMIC);
-		if (ptmpchar == NULL)
+		if (!ptmpchar)
 			return ret;
 
 		ptx_desc = (struct tx_desc *)(ptmpchar + FWBUFF_ALIGN_SZ -