Check calloc's return value before using the pointer

If calloc fails, bail out immediately instead of trying to
use the NULL pointer.
Signed-off-by: Michael Heimpold <michael.heimpold@i2se.com>
Cc: Michael Heimpold <mhei@heimpold.de>
Reviewed-by: Avri Altman <avri.altman@wdc.com>
Signed-off-by: Chris Ball <chris@printf.net>

lsmmc.c

@@ -374,6 +374,8 @@ char *to_binstr(char *hexstr)
 	char *binstr;
 
 	binstr = calloc(strlen(hexstr) * 4 + 1, sizeof(char));
+	if (!binstr)
+		return NULL;
 
 	while (hexstr && *hexstr != '\0') {
 		if (!isxdigit(*hexstr))