[asan][mips] Adding support of asan for mipsel arch

cmake/config-ix.cmake: Enabled building of asan for mipsel arch
test/asan/CMakeLists.txt: Enabled testing of asan for mipsel

Patch by Kumar Sukhani

Differential Revision: http://reviews.llvm.org/D5615


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@219496 91177308-0d34-0410-b5e6-96231b3b80d8