ArmPlatformPkg: create hw-agnostic LcdGraphicsOutputDxe driver

ArmPlatformPkg: create hw-agnostic LcdGraphicsOutputDxe driver

Create a new LcdGraphicsOutputDxe driver from the existing sources that
takes its hardware abstractions from a LcdHwLib library instance rather
than from a .c file linked directly. All we need is a new .inf file, and
a minimal tweak to LcdGraphicsOutputDxe.h to reuse the LcdHwlib prototypes
rather than open code them.

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>
[ardb: add it to ArmPlatformPkg.dsc so we can build test it standalone]
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>