aco/ra: Fix counting of subdword variables in get_reg_create_vector
The loop variable "k" shadowed another variable in the outer scope, so this loop had no actual effect.
Fixes: 52cc1f82 ("aco: improve p_create_vector RA for sub-dword operands")
PERCENTAGE DELTAS Shaders CodeSize Instrs Cycles Copies
youngblood_fp16 682 -0.00% -0.00% -0.00% -0.00%
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All affected 1 -0.08% -0.05% -0.07% -0.57%
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Total 136546 -0.00% -0.00% -0.00% -0.00%