ShellPkg: acpiview: Add support for parsing FACS

ShellPkg: acpiview: Add support for parsing FACS

Add support for parsing the ACPI FACS table.

The FADT parser has also been updated as it
links the FACS table using the FIRMWARE_CTRL
or X_FIRMWARE_CTRL fields.

Since the FACS table does not follow the standard
ACPI header, the FADT parser extracts the FACS
signature, length and version fields before invoking
the FACS parser.

Cc: Ray Ni <ray.ni@intel.com>
Cc: Zhichao Gao <zhichao.gao@intel.com>
Reviewed-by: Zhichao Gao <zhichao.gao@intel.com>
Signed-off-by: Sami Mujawar <sami.mujawar@arm.com>