[MIPS] Link .dex or .oat code lacking .MIPS.abiflags segment

This corrects an issue with mips32 Art on mips64r6 Android, where
Java ran slowly due to unintended use of kernel-trap emulation of
single-precision floating point registers. This also regressed all
Art tests due to an extra logcat line
    WARNING: linker: Using FRE=1 mode to run "..."

When targeting mips32r6, Art generates modeless or FR=1 floating point
code, same as Android's own native mips32r6 modules. So the trapping was
unneeded. Linker was confusing Art-generated modules with those from
old NDK compilers, which do need that trapping mode.

This linker filename check may become unnecessary, if Art learns how to
generate .MIPS.abiflags segments in its generated elf-like codefiles.

Change-Id: I18069d1234960c680c5df739514da09015a7fdb6