ACPICA: New: acpi_get_gpe_device interface

This function maps an input GPE index to a GPE block device. Also
Added acpi_current_gpe_count to track the current number of GPEs
that are being managed by the ACPICA core (both FADT-based GPEs
and the GPEs contained in GPE block devices.)

Modify drivers/acpi/system.c to use these 2 new interfaces

Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/include/acpi/acglobal.h b/include/acpi/acglobal.h
index 90cc820..78f3c14 100644
--- a/include/acpi/acglobal.h
+++ b/include/acpi/acglobal.h
@@ -326,6 +326,7 @@
 ACPI_EXTERN struct acpi_gpe_xrupt_info *acpi_gbl_gpe_xrupt_list_head;
 ACPI_EXTERN struct acpi_gpe_block_info
 *acpi_gbl_gpe_fadt_blocks[ACPI_MAX_GPE_BLOCKS];
+ACPI_EXTERN u32 acpi_current_gpe_count;
 
 /*****************************************************************************
  *