binutils: testsuite: avoid dup names when using multiple as: directives

binutils tests support running a test with distinct options to the
assembler by allowing

	#as: <optset-1>
	#as: <optset-2>

But results in both test runs using the same test name in the summary
file.  This causes confusion if one test fails but the other doesn't
(and GCC's compare_tests script will diagnose this as an error).  To
fix the ambiguity append the appropriate optset to the test name.

We only do this if a test has multiple runs in this way to avoid
causing every test result name to change.