ArmPlatformPkg: Add PCD to select pixel format

ArmPlatformPkg: Add PCD to select pixel format

Current HDLCD and PL111 platform libraries do not support display modes
with PixelBlueGreenRedReserved8BitPerColor format, i.e. because of
historical confusion, they do not support the UEFI default
PixelBlueGreenRedReserved8BitPerColor format

In LcdPlatformLib for PL111, LcdPlatformQueryMode returns the pixel
format as PixelRedGreenBlueReserved8BitPerColor which is wrong, because
that does not match the display controller's pixel format which is set
to BGR in PL111Lcd LcdHwLib.

Also it is not possible to configure pixel format as RGB/BGR for the
display modes for a platform at build time.

This change adds PcdGopPixelFormat to configure pixel format as
    PixelRedGreenBlueReserved8BitPerColor    or
    PixelBlueGreenRedReserved8BitPerColor    or
    PixelBitMask.
With this change, pixel format can be selected in the platform specific
.dsc file for all supported display modes.

Support for PixelBitMask is not implemented in PL111 or HDLCD LcdHwLib
libraries, hence  HDLCD and PL111 platform libraries will return error
EFI_UNSUPPORTED if PcdGopPixelFormat is set to PixelBitMask.  Indeed,
it is not clear what selecting PixelBitMask might mean, but the option
is allowed as it might suit a custom platform.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Girish Pathak <girish.pathak@arm.com>
Signed-off-by: Evan Lloyd <evan.lloyd@arm.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>