Revert "gpio: mxc: Unlock on error path in mxc_flip_edge()"

This reverts commit 621f296f which is
commit 37870358 upstream.

It needs to be reverted, as a later commit breaks the ABI and that is
not needed in the Android kernel tree.

Bug: 161946584
Change-Id: Ibec377e5d83f554f1dce645b8b43197acbd4036a
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>