st/mesa: fix swizzle issue in st_create_sampler_view_from_stobj()

st/mesa: fix swizzle issue in st_create_sampler_view_from_stobj()

Some demos, like Heaven, were creating and destroying a large number
of sampler views because of a swizzle issue.

Basically, we compute the sampler view's swizzle by examining the
texture format, user swizzle, depth mode, etc.  Later, during validation
we recompute that swizzle (in case something like depth mode changes)
and see if it matches the view's swizzle.

In the case of PIPE_FORMAT_RGTC2_UNORM, get_texture_format_swizzle
returned SWIZZLE_XYZW but the u_sampler_view_default_template() function
was setting the sampler view's swizzle to SWIZZLE_XY01.  This mismatch
caused the validation step to always "fail" so we'd destroy the old
sampler view and create a new one.

By removing the conditional, the sampler view's swizzle and the computed
texture swizzle match and validation "passes".  When creating a new sampler
view, we always want to use the texture swizzle which we just computed.

Fixes VMware issue 1733389.

Cc: mesa-stable@lists.freedesktop.org
Reviewed-by: Charmaine Lee <charmainel@vmware.com>