drm/omap: Open code phys_to_page()

phys_to_page() is not available on most architectures.
Just open code it like msm does. Allows COMPILE_TEST=y
builds of omapdrm on other architectures.

Cc: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240408170426.9285-15-ville.syrjala@linux.intel.comReviewed-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>

drivers/gpu/drm/omapdrm/omap_gem.c

@@ -1022,8 +1022,8 @@ struct sg_table *omap_gem_get_sg(struct drm_gem_object *obj,
 
 	if (addr) {
 		for_each_sg(sgt->sgl, sg, count, i) {
-			sg_set_page(sg, phys_to_page(addr), len,
-				offset_in_page(addr));
+			sg_set_page(sg, pfn_to_page(__phys_to_pfn(addr)),
+				    len, offset_in_page(addr));
 			sg_dma_address(sg) = addr;
 			sg_dma_len(sg) = len;