LD/testsuite: run_dump_test: Use the intended test name ASAP

LD/testsuite: run_dump_test: Use the intended test name ASAP

Bring the LD implementation of `run_dump_test' in line with its binutils
and GAS counterparts and use the intended test name, from the `name' tag
if set, for test status reporting as soon as it is available.

	ld/
	* testsuite/lib/ld-lib.exp (run_dump_test): Move the setting of
	`testname' earlier on and use it for test status reporting.