intel/isl/gen7: Don't allow multisampled surfaces with valign2

intel/isl/gen7: Don't allow multisampled surfaces with valign2

There is the same constraintg later on as assert in
isl_gen7_choose_image_alignment_el() so catch it earlier in order
to return error instead of crash.

Needed to avoid crashes with piglits on IVB and HSW:

arb_internalformat_query2.image_format_compatibility_type pname checks
arb_internalformat_query2.all internalformat_<x>_type pname checks
arb_internalformat_query2.max dimensions related pname checks
arb_copy_image.arb_copy_image-formats --samples=2/4/6/8
arb_texture_float.multisample-fast-clear gl_arb_texture_float

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Signed-off-by: Topi Pohjolainen <topi.pohjolainen@intel.com>