intel/isl: Fix up asserts in calc_phys_level0_extent_sa

intel/isl: Fix up asserts in calc_phys_level0_extent_sa

The assertion that a format is uncompressed in the multisample layouts
isn't quite right.  What we really want to assert is that the format
supports multisampling which is a bit more complicated query.  We also want
to assert that it has a block size of 1x1 since we do nothing with the
block size in the phys_level0_sa assignment.

Signed-off-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Topi Pohjolainen <topi.pohjolainen@intel.com>
Reviewed-by: Chad Versace <chadversary@chromium.org>
Reviewed-by: Nanley Chery <nanley.g.chery@intel.com>