arm: u8500: Imply options for new drivers

Imply the options for new drivers added for ARM U8500 during the
U-Boot 2021.10 merge window. Adding these as "imply" in the Kconfig
avoids having to add them to all the board defconfigs but still allows
disabling them if wanted.

Also select DM_USB_GADGET if DM_USB is selected because otherwise
the Ux500 MUSB glue driver does not show up in the configuration.

Signed-off-by: Stephan Gerhold <stephan@gerhold.net>