bootstage: Drop BOOTSTAGE_ID_FIT_KERNEL_INFO

This is a misnomer since we don't necessarily know that the image is a
FIT. Use the existing BOOTSTAGE_ID_CHECK_IMAGETYPE instead.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>

boot/bootm.c

@@ -233,7 +233,7 @@ static int boot_get_kernel(const char *cmd_name, const char *addr_fit,
 #endif
 	default:
 		printf("Wrong Image Format for %s command\n", cmd_name);
-		bootstage_error(BOOTSTAGE_ID_FIT_KERNEL_INFO);
+		bootstage_error(BOOTSTAGE_ID_CHECK_IMAGETYPE);
 		return -EBADF;
 	}