Add mips32 r1 to the list of supported targets for Mips fast-isel

Summary:
Expand list of supported targets for Mips to include mips32 r1.
Previously it only include r2. More patches are coming where there is 
a difference but in the current patches as pushed upstream, r1 and r2
are equivalent.

Test Plan:
simplestorefp1.ll

add new build bots at mips to test this flavor at both -O0 and -O2

Reviewers: dsanders

Reviewed By: dsanders

Differential Revision: http://reviews.llvm.org/D5306

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217821 91177308-0d34-0410-b5e6-96231b3b80d8