[libomptarget][amdgpu][nfc] Fix build on centos

[libomptarget][amdgpu][nfc] Fix build on centos

rtl.cpp replaced 224 with a #define from elf.h, but that
doesn't work on a centos 7 build machine with an old elf.h

Reviewed By: ronlieb

Differential Revision: https://reviews.llvm.org/D94528