[HIP] Fix device only linking for -fgpu-rdc

Currently when -fgpu-rdc is specified, HIP toolchain always does host linking even
if --cuda-device-only is specified.

This patch fixes that. Only device linking is performed when --cuda-device-only
is specified.

Reviewed by: Artem Belevich

Differential Revision: https://reviews.llvm.org/D116840