drm/i915: Add MIPI mmio reg base

This patch adds a mmio base address variable for DSI display,
to make the DSI code generic, so that, if required, the same code
can be re-used for future platforms with different mmio base.

Signed-off-by: Shashank Sharma <shashank.sharma@intel.com>
Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>
[danvet: Appease checkpatch.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_drv.h

@@ -1360,6 +1360,9 @@ struct drm_i915_private {
 	 */
 	uint32_t gpio_mmio_base;
 
+	/* MMIO base address for MIPI regs */
+	uint32_t mipi_mmio_base;
+
 	wait_queue_head_t gmbus_wait_queue;
 
 	struct pci_dev *bridge_dev;