Fix swizzle on rhs in some cases.

Noticed in ps4\primID test shader.
Output0.yzw = vec4(Temp0.xxxx * vec4(0.000000, 2.000000, 0.015625,
0.031250)).xyz;
but should be
Output0.yzw = vec4(Temp0.xxxx * vec4(0.000000, 2.000000, 0.015625,
0.031250)).yzw;