intel: Refactor the wrapping of textures with renderbuffers

intel: Refactor the wrapping of textures with renderbuffers

Before this commit, the renderbuffer's region was updated in
intel_renderbuffer_texture(). This commit moves the update into
intel_update_wrapper(), which is a more logical location for updates.

This is in preparation for the next commit, which allocates and
updates the texture's hiz region in intel_update_wrapper(). Having the two
region updates located in the same function makes good form.

Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Chad Versace <chad@chad-versace.us>