[Power9] Added support for the modsw, moduw, modsd, modud hardware instructions.

Note that if we need the result of both the divide and the modulo then we
compute the modulo based on the result of the divide and not using the new
hardware instruction.

Commit on behalf of STEFAN PINTILIE.
Differential Revision: https://reviews.llvm.org/D33940

llvm-svn: 305210