The function `polarSu3` uses `sincos` instead of `sincospi`

[weinbe2]

As the title notes, the function polarSu3 in su3_project.cuh uses a quda::sincos call here: https://github.com/lattice/quda/blob/develop/include/su3_project.cuh#L106

This could be replaced with a sincospi, improving performance and reducing/eliminating the stack frame in some routines that utilize it.