[OpenMP] fix clang warning about printf format in CUDA plugin

Summary: Warnings are printed by clang when building LIBOMPTARGET_ENABLE_DEBUG=ON due incorrect format string.

Reviewers: tianshilei1992, jdoerfert

Reviewed By: tianshilei1992

Subscribers: yaxunl, guansong, sstefan1, openmp-commits

Tags: #openmp

Differential Revision: https://reviews.llvm.org/D82789