ACPICA: Remove the VRTC table

ACPICA commit 4534cc3700f73c88e2f6a0e0f0b9efe4fc644757

The VRTC table is no longer in use and is not defined by the ACPI
specification.  Remove the table from the known, allowed tables.

Link: https://github.com/acpica/acpica/commit/4534cc37


Signed-off-by: Al Stone <ahs3@ahs3.net>
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Erik Kaneda <erik.kaneda@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>