ACPI / APEI: Remove spurious GHES_TO_CLEAR check

ghes_notify_nmi() checks ghes->flags for GHES_TO_CLEAR before going
on to __process_error(). This is pointless as ghes_read_estatus()
will always set this flag if it returns success, which was checked
earlier in the loop. Remove it.

Signed-off-by: James Morse <james.morse@arm.com>
Reviewed-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>