sysfb: Add struct sysfb_display_info

sysfb: Add struct sysfb_display_info

Add struct sysfb_display_info to wrap display-related state. For now
it contains only the screen's video mode. Later EDID will be added as
well.

This struct will be helpful for passing display state to sysfb drivers
or from the EFI stub library.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Richard Lyu <richard.lyu@suse.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>