drm/i915/skl: Extract tile height code into a helper function

It will be used in a later patch and also convert all height parameters
from int to unsigned int.

v2: Rebased for fb modifiers.
v3: Fixed v2 rebase.
v4:
   * Height should be unsigned int.
   * Make it take pixel_format for consistency and simplicity.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Michel Thierry <michel.thierry@intel.com> (v1)
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> (v4)
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index d2a4de0..e974dd6 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -901,9 +901,10 @@
 	intel_frontbuffer_flush(dev, frontbuffer_bits);
 }
 
-int intel_fb_align_height(struct drm_device *dev, int height,
-			  uint32_t pixel_format,
-			  uint64_t fb_format_modifier);
+unsigned int intel_fb_align_height(struct drm_device *dev,
+				   unsigned int height,
+				   uint32_t pixel_format,
+				   uint64_t fb_format_modifier);
 void intel_fb_obj_flush(struct drm_i915_gem_object *obj, bool retire);
 
 u32 intel_fb_stride_alignment(struct drm_device *dev, uint64_t fb_modifier,