MIPS: Define GCR_GIC_STATUS register fields

MIPS: Define GCR_GIC_STATUS register fields

Add definitions for the GICEX field in the GCR_GIC_STATUS register to
mips-cm.h for use in a later patch.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: devicetree@vger.kernel.org
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Pawel Moll <pawel.moll@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Ian Campbell <ijc+devicetree@hellion.org.uk>
Cc: Kumar Gala <galak@codeaurora.org>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: linux-kernel@vger.kernel.org
Patchwork: http://patchwork.linux-mips.org/patch/10112/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>