[mips] Correct linux dynamic linker for -mnan=2008

Summary:
The dynamic linker is named ld-linux-mipsn8.so.1 when -mnan=2008 is given (or
is the default). It remains ld.so.1 for other cases.

This is necessary for MIPS32r6/MIPS64r6 since these ISA's default to -mnan=2008.

Differential Revision: http://reviews.llvm.org/D4273


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@211598 91177308-0d34-0410-b5e6-96231b3b80d8