[committed] Fix expected output for various MIPS multiplication tests

[committed] Fix expected output for various MIPS multiplication tests

The recent multiply-highpart work twiddled code generation on the MIPS targets
and is causing mips.exp failures.

The resultant code is actually better and matches a comment in the test files
which indicates that it would be better to generate a mult-highpart.  So I'm
pretty confident in removing the undesired mflo & changing the name of the
target pattern we expect to see.

This fixes the mips64 and mips64el failures in my tester.  I suspect it'll
also fix the failures on mipsisa32, but that target is bootstrapped with qemu --
which takes forever so it only runs once a week ;-)

gcc/testsuite
	* gcc.target/mips/fix-r4000-2.c: Update expected output.
	* gcc.target/mips/fix-r4000-3.c: Update expected output.  Add
	-fexpensive-optimizations for consistency in output.
	* gcc.target/mips/fix-r4000-7.c: Update expected output.
	* gcc.target/mips/fix-r4000-8.c: Update expected output.