ArmPlatformPkg: Redefine LcdPlatformGetTimings function

ArmPlatformPkg: Redefine LcdPlatformGetTimings function

The LcdPlatformGetTimings interface function takes similar sets of
multiple parameters for horizontal and vertical timings which can be
aggregated in a common data type. This change defines a structure
SCAN_TIMINGS for this which can be used to describe both horizontal and
vertical scan timings, and accordingly redefines the
LcdPlatformGetTiming interface, greatly reducing the amount of data
passed about.

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>