drm/i915: Add i915_gem_object_create_from_data()

i915_gem_object_create_from_data() is a generic function to save data
from a plain linear buffer in a new pageable gem object that can later
be accessed by the CPU and/or GPU.

We will need this for the microcontroller firmware loading support code.

Derived from i915_gem_object_write(), originally by Alex Dai

v2:
    Change of function: now allocates & fills a new object, rather than
        writing to an existing object
    New name courtesy of Chris Wilson
    Explicit domain-setting and other improvements per review comments
        by Chris Wilson & Daniel Vetter

v4:
    Rebased

Issue: VIZ-4884
Signed-off-by: Alex Dai <yu.dai@intel.com>
Signed-off-by: Dave Gordon <david.s.gordon@intel.com>
Reviewed-by: Tom O'Rourke <Tom.O'Rourke@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 23ce125e..77c2379 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2758,6 +2758,8 @@
 			 const struct drm_i915_gem_object_ops *ops);
 struct drm_i915_gem_object *i915_gem_alloc_object(struct drm_device *dev,
 						  size_t size);
+struct drm_i915_gem_object *i915_gem_object_create_from_data(
+		struct drm_device *dev, const void *data, size_t size);
 void i915_init_vm(struct drm_i915_private *dev_priv,
 		  struct i915_address_space *vm);
 void i915_gem_free_object(struct drm_gem_object *obj);