Revert "gpio: mxc: Protect GPIO irqchip RMW with bgpio spinlock"

This reverts commit 8335f877 which is
commit e5464277 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
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: Ic58e4907c6e2dede207f6c1466bd30750d464624