[Compiler-rt][MIPS][Profile] Adding support for MIPS32/64

Summary:
Changed cmake/config-ix.cmake to add support for different MIPS architectures: mips, mipsel, mips64, mips64el
In profile code there is no target  based dependencies, so just enabling mips flag does the work.

Patch by Mohit Bhakkad

Reviewers: dsanders, void, petarj, kcc, samsonov

Reviewed By: samsonov

Subscribers: llvm-commits, farazs, kumarsukhani

Differential Revision: http://reviews.llvm.org/D4880