broadcom/vc5: Fix up channel swizzling for textures on 4.x.

broadcom/vc5: Fix up channel swizzling for textures on 4.x.

I had 3.x putting swizzling in the texture state only for 16-bit texture
returns, and in the shader for 32-bit.  This may be due to having mixed up
the return channel setup on 3.x back before I had moved it into the
compiler.  On 4.x, the non-border-color texwrap tests are passing nicely
with both 16 and 32-bit returns with swizzling in the texture state.