i2c: piix4: Fix a memory leak in the EFCH MMIO support

The recently added support for EFCH MMIO regions introduced a memory
leak in that code path. The leak is caused by the fact that
release_resource() merely removes the resource from the tree but does
not free its memory. We need to call release_mem_region() instead,
which does free the memory. As a nice side effect, this brings back
some symmetry between the legacy and MMIO paths.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Reported-by: Yi Zhang <yi.zhang@redhat.com>
Tested-by: Yi Zhang <yi.zhang@redhat.com>
Reviewed-by: Terry Bowman <terry.bowman@amd.com>
Tested-by: Terry Bowman <Terry.Bowman@amd.com>
Fixes: 7c148722

 ("i2c: piix4: Add EFCH MMIO support to region request and release")
Signed-off-by: Wolfram Sang <wsa@kernel.org>