radeonsi: fix HTILE for NPOT textures with mipmapping on SI/CI

VI uses addrlib so it's unaffected.

Cc: 18.1 18.2 <mesa-stable@lists.freedesktop.org>
Tested-by: Dieter Nützel <Dieter@nuetzel-hh.de>
(cherry picked from commit a1b9a00f)
Conflicts resolved by Dylan

Conflicts:
	src/gallium/drivers/radeonsi/si_texture.c