mtd: uboot: Add meaningful error message

The current error message in get_part if CONFIG_MTDPARTS is disabled is
"offset is not a number" which is confusing and doesn't help at all.

Change that for something that might give a hint on what's going on.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
1 file changed