Function uacpi_mask_gpe

Hard mask/umask a general purpose event at 'idx' managed by 'gpe_device'.

This is used to permanently silence an event so that further calls to enable/disable as well as suspend/resume get ignored. This might be necessary for GPEs that cause an event storm due to the kernel's inability to properly handle them. The only way to enable a masked event is by a call to unmask. NOTE: 'gpe_device' may be null for GPEs managed by _GPE