btrfs-progs: Fix getopt on arm/ppc platforms

(same as commit bb0eabc383)
There, 'char' is unsigned, so once assigned '-1' from getopt, it gets
the value 255. Then, it compared to '-1' gives false.

Signed-off-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

btrfs-crc.c

@@ -34,7 +34,7 @@ void usage(void)
 
 int main(int argc, char **argv)
 {
-	char c;
+	int c;
 	unsigned long checksum = 0;
 	char *str;
 	char *buf;

cmds-device.c

@@ -294,7 +294,7 @@ static int cmd_dev_stats(int argc, char **argv)
 	int ret;
 	int fdmnt;
 	int i;
-	char c;
+	int c;
 	int err = 0;
 	__u64 flags = 0;