libpayload/drivers: Fix mem-leak in cbmem_console error condition

When returning from cbmem_console_snapshot() because of a corrupted
console structure, the memory that was just allocated was not being
freed as it "should be".

BUG=CID 1419477

Signed-off-by: Martin Roth <gaumless@gmail.com>
Change-Id: I85370fb49c9ef9a00cd2ea516fa80c9e152c9b48
Reviewed-on: https://review.coreboot.org/c/coreboot/+/88334
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Elyes Haouas <ehaouas@noos.fr>

payloads/libpayload/drivers/cbmem_console.c

@@ -126,6 +126,7 @@ char *cbmem_console_snapshot(void)
 	if (overflow) {
 		if (cursor >= size) {
 			printf("ERROR: CBMEM console struct is corrupted\n");
+			free(console_c);
 			return NULL;
 		}
 		for (oldc = cursor; oldc < size; oldc++)