colibri-imx6ull: configuration clean-up

Drop disabling SPL_SYS_THUMB_BUILD as we anyway do not use SPL.
Enbale CRC32 verify, USB SDP and EFI loader support.
Drop CMD_GPT and disabling RANDOM_UUID.
Do savedefconfig which drops USB_FUNCTION_SDP.

Signed-off-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Reviewed-by: Igor Opaniuk <igor.opaniuk@toradex.com>