[libomptarget][nvptx] Reduce calls to cuda header

[libomptarget][nvptx] Reduce calls to cuda header

Remove use of clock_t in favour of a builtin. Drop a preprocessor branch.

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D94731

GitOrigin-RevId: 214387c2c694c92fec713f7ad224f10c1aebc1cf
1 file changed