softpipe: Clamp border colors when needed

softpipe: Clamp border colors when needed

unorm and snorm require that the border color values are clamped, so when
picking the sampler view copy/clamp the border color from the sampler and
use these adjusted values.

Fixes:

  dEQP-GLES31.functional.texture.border_clamp.range_clamp.linear_compressed_color
  dEQP-GLES31.functional.texture.border_clamp.range_clamp.linear_snorm_color
  dEQP-GLES31.functional.texture.border_clamp.range_clamp.linear_srgb_color
  dEQP-GLES31.functional.texture.border_clamp.range_clamp.linear_unorm_color
  dEQP-GLES31.functional.texture.border_clamp.range_clamp.nearest_compressed_color
  dEQP-GLES31.functional.texture.border_clamp.range_clamp.nearest_snorm_color
  dEQP-GLES31.functional.texture.border_clamp.range_clamp.nearest_srgb_color
  dEQP-GLES31.functional.texture.border_clamp.range_clamp.nearest_unorm_color
  dEQP-GLES31.functional.texture.border_clamp.range_clamp.nearest_unorm_depth
  dEQP-GLES31.functional.texture.border_clamp.range_clamp.nearest_unorm_depth_uint_stencil_sample_depth

Signed-off-by: Gert Wollny <gert.wollny@collabora.com>
Reviewed-by: Roland Scheidegger <sroland@vmware.com>