btrfs-progs: sb-mod: clean up used memory

ASAN build reports that there are some leaks:

Direct leak of 7 byte(s) in 1 object(s) allocated from:
    #0 0x7f7fa15200e4 in strdup (/lib64/libasan.so.8+0x1200e4)
    #1 0x000000579d7e in main /home/ds/x/g/btrfs-progs/btrfs-sb-mod.c:417
    #2 0x7f7fa102b2fa in __libc_start_call_main (/lib64/libc.so.6+0x2b2fa)
    #3 0x7ffce11eee69  ([stack]+0x20e69)
SUMMARY: AddressSanitizer: 7 byte(s) leaked in 1 allocation(s).

It's the operation name, so free it after it's processed.

Signed-off-by: David Sterba <dsterba@suse.com>

Author: kdave

btrfs-sb-mod.c

@@ -95,7 +95,7 @@ enum field_op {
 };
 
 struct fspec {
-	const char *name;
+	char *name;
 	enum field_op fop;
 	u64 value;
 };
@@ -427,6 +427,7 @@ int main(int argc, char **argv)
 		sb_edit(sb, &spec[i]);
 		if (op_is_write(spec[i].fop))
 			changed = 1;
+		free(spec[i].name);
 	}
 
 	if (changed) {