MdeModulePkg AcpiTableDxe: Cover EFI_ACPI_TABLE_VERSION_5_0.

MdeModulePkg AcpiTableDxe: Cover EFI_ACPI_TABLE_VERSION_5_0.

Follow PI 1.4 spec,
1. Cover EFI_ACPI_TABLE_VERSION_5_0.
2. Update TableKey parameter description in the
EFI_ACPI_SDT_PROTOCOL.GetAcpiTable() section.
3. Update EFI_ACPI_SDT_PROTOCOL.GetAcpiTable() description.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@17649 6f19259b-4bc3-4df7-8a09-765794883524