RISC-V LLVM was only implement small/medlow code model, so it defined
__riscv_cmodel_medlow directly without check.
Now, we have medium/medany code model in RISC-V back-end, it should
define according the actually code model.
Reviewed By: lewis-revill
Differential Revision: https://reviews.llvm.org/D67065
llvm-svn: 372078