meta: Actually initialize ImmutableLevels to 1.

meta: Actually initialize ImmutableLevels to 1.

Otherwise, ImmutableLevels is 0, which is an illegal value.  Later,
_mesa_meta_setup_sampler will use _mesa_texture_parameteriv to set

   texObj->MaxLevel = CLAMP(params[0], texObj->BaseLevel,
                            texObj->ImmutableLevels - 1);

which turns into a completely bogus CLAMP(value, 0, -1)...where the
upper bound is smaller than the lower bound.  This ends up being -1
today due to the way CLAMP is implemented, which is a bogus MaxLevel.

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>