ACPICA: WSMT: Fix typo, no functional change

ACPICA commit 764d18c5a83949ff3b0dbda6055cee1929b9caa2

The table signature WSMT stands for "Windows SMM Mitigations Table".
It is not "Windows SMM Migrations Table".

Link: https://github.com/acpica/acpica/commit/764d18c5


Reported-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Erik Kaneda <erik.kaneda@intel.com>
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>