spi: spidev_test: Fix input file check when transferring file

Check the input file fd instead of spidev fd.
The spidev fd is supposed to be OK otherwise the transfer_file() function
would not be called at all.
Signed-off-by: NMichal Vokáč <vokac.m@gmail.com>
Reviewed-by: NJoshua Clayton <stillcompiling@gmail.com>
Signed-off-by: NMark Brown <broonie@kernel.org>

tools/spi/spidev_test.c

@@ -315,7 +315,7 @@ static void transfer_file(int fd, char *filename)
 		pabort("can't stat input file");
 
 	tx_fd = open(filename, O_RDONLY);
-	if (fd < 0)
+	if (tx_fd < 0)
 		pabort("can't open input file");
 
 	tx = malloc(sb.st_size);