ACPICA: Improve exception handling for GPE block installation.

1) Return an actual status value from acpi_ev_get_gpe_xrupt_block.
2) Don't clobber the status when exiting acpi_ev_install_gpe_block.

References: https://bugs.acpica.org/show_bug.cgi?id=1019
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>