x86/EFI: retrieve EDID

x86/EFI: retrieve EDID

When booting directly from EFI, obtaining this information from EFI is
the only possible way. And even when booting with a boot loader
interposed, it's more clean not to use legacy BIOS calls for this
purpose. (The downside being that there are no "capabilities" that we
can retrieve the EFI way.)

To achieve this we need to propagate the handle used to obtain the
EFI_GRAPHICS_OUTPUT_PROTOCOL instance for further obtaining an
EFI_EDID_*_PROTOCOL instance, which has been part of the spec since 2.5.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Luca Fancellu <luca.fancellu@arm.com> # Arm, common
Acked-by: Roger Pau Monné <roger.pau@citrix.com>
Acked-by: Bertrand Marquis <bertrand.marquis@arm.com> #arm