platform/x86/amd: pmc: Use release_mem_region() to undo request_mem_region_muxed()

Muxed (mem) regions will wait in request_mem_region_muxed() if the region
is busy (in use by another consumer) during the call.

In order to wake-up possibly waiting other consumers of the region,
it must be released by a release_mem_region() call, which will actually
wake up any waiters.

release_mem_region() also frees the resource created by
request_mem_region_muxed(), avoiding the need for the unmatched kfree().

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
Link: https://lore.kernel.org/r/20230711095920.264308-1-hdegoede@redhat.com