OutOfBandManagement/SpcrFeaturePkg: PCD based IRQ/GSI

Create a new PCD to hold the IRQ or GSI number for SPCR,
with default values of 4.
Update the ACPI SPCR table's IRQ value based on PCD.

Cc: Sai Chaganty <rangasai.v.chaganty@intel.com>
Cc: Isaac Oram <isaac.w.oram@intel.com>
Reviewed-by: Nate DeSimone <nathaniel.l.desimone@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Abner Chang <abner.chang@amd.com>
Signed-off-by: Abdul Lateef Attar <AbdulLateef.Attar@amd.com>

Change-Id: I7218903fa5572f8139ad45db598ab085f079713b