i965/vs: Rename "sampler" to "texunit" in texturing code.
i965/vs: Rename "sampler" to "texunit" in texturing code.

The number we're passing around is actually the ID of the texture unit,
as opposed to the numerical value our of sampler uniforms.  Calling it
"texunit" clarifies this slightly.

Signed-off-by: Kenneth Graunke <bd2562f754ec92342f93f61c25d731e290a2ffa8@whitecape.org>
Reviewed-by: Paul Berry <de21b9f22e6dd0bdf7890875d6e07ef4967c44ce@gmail.com>
Reviewed-by: Ian Romanick <2b237cafb16dc45038e85df6c85e74e6d899eba9@intel.com>
Reviewed-by: Eric Anholt <96f164ad4d9b2b0dacf8ebee2bb1eeb3aa69adf1@anholt.net>

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