i965 new VS: Fix src_reg(uint32_t) constructor.
i965 new VS: Fix src_reg(uint32_t) constructor.

This constructor was storing its argument in the wrong field of the
"imm" enum, resulting in it being converted to a float when it should
have remained an unsigned integer.  This was preventing clipping from
working properly on pre-GEN6.

Reviewed-by: Kenneth Graunke <bd2562f754ec92342f93f61c25d731e290a2ffa8@whitecape.org>

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