splash_source: add support for filesystem formatted usb

Add support for loading splash image from USB drive formatted with a
filesystem.

Cc: Igor Grinberg <grinberg@compulab.co.il>
Cc: Tom Rini <trini@konsulko.com>
Signed-off-by: Nikita Kiryanov <nikita@compulab.co.il>
2 files changed