[mips] Small update to the implementation of eh.return for Mips.

[mips] Small update to the implementation of eh.return for Mips.

This patch initializes t9 to the handler address, but only if the relocation
model is pic. This handles the case where handler to which eh.return jumps
points to the start of the function.

Patch by Sasa Stankovic.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@178588 91177308-0d34-0410-b5e6-96231b3b80d8