[HIP] Generate offloading entries for HIP with the new driver.

This patch adds the small change required to output offloading entried
for HIP instead of CUDA. These should be placed in different sections so
because they need to be distinct to the offloading toolchain, otherwise
we'd have HIP trying to register CUDA kernels or vice-versa. This patch will
precede support for HIP in the linker wrapper.

Reviewed By: yaxunl, tra

Differential Revision: https://reviews.llvm.org/D128850