staging: gpib: use int type to store negative error codes

The "ret" variable is used to store the return from bb_write() returns
either zero on success or negative error codes on failure. Storing the
error codes in size_t which is an unsigned long, doesn't cause an issue
at runtime but it's ugly as pants. Change "ret" from size_t to int
type. No effect on runtime.

Signed-off-by: Qianfeng Rong <[e-mail]>
Reviewed-by: Dan Carpenter <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/staging/gpib/gpio/gpib_bitbang.c

···
 static int bb_command(struct gpib_board *board, u8 *buffer,
 		      size_t length, size_t *bytes_written)
 {
-	size_t ret;
+	int ret;
 	struct bb_priv *priv = board->private_data;
 	int i;