ACPI: Fix possible recursive locking in hwregs.c

ACPI: Fix possible recursive locking in hwregs.c

Calling pm-suspend might trigger a recursive lock in it's code path.
In function acpi_hw_clear_acpi_status, acpi_os_acquire_lock holds
the lock acpi_gbl_hardware_lock before calling acpi_hw_register_write(),
then without releasing acpi_gbl_hardware_lock, this function calls
acpi_ev_walk_gpe_list, which tries to hold acpi_gbl_gpe_lock.
Both acpi_gbl_hardware_lock and acpi_gbl_gpe_lock are at same
lock-class and which might cause lock recursion deadlock.

Following patch fixes this scenario by just releasing
acpi_gbl_hardware_lock before calling acpi_ev_walk_gpe_list.

 Changes since v0(https://lkml.org/lkml/2011/9/21/355):
	- Fix changelog, thanks to Lin Ming.

 Changes since v1 (https://lkml.org/lkml/2011/11/3/89):
	- Update changelog and rename goto label, courtesy Srivatsa S. Bhat.

Signed-off-by: Rakib Mullick <rakib.mullick@gmail.com>
Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Acked-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Len Brown <len.brown@intel.com>