MIPS/GAS/testsuite: Remove last remnants of ECOFF support

MIPS/GAS/testsuite: Remove last remnants of ECOFF support

Complement commit 16e5e222b6ea ("Make gas/mips/mips.exp ELF-only"),
<https://sourceware.org/ml/binutils/2013-06/msg00195.html>, and commit
fcedb9f3ca87 ("MIPS/GAS/testsuite: Remove remnants of a.out/ECOFF
support"), and remove stale ECOFF test dumps previously missed.

	gas/
	* testsuite/gas/mips/r3900@ecoff@ld.d: Remove test.
	* testsuite/gas/mips/mips2@ecoff@ld.d: Remove test.
	* testsuite/gas/mips/mips32@ecoff@ld.d: Remove test.
	* testsuite/gas/mips/mips32r2@ecoff@ld.d: Remove test.
	* testsuite/gas/mips/r3900@ecoff@ld-forward.d: Remove test.
	* testsuite/gas/mips/mips2@ecoff@ld-forward.d: Remove test.
	* testsuite/gas/mips/mips32@ecoff@ld-forward.d: Remove test.
	* testsuite/gas/mips/mips32r2@ecoff@ld-forward.d: Remove test.
	* testsuite/gas/mips/mips1@ecoff@sd.d: Remove test.
	* testsuite/gas/mips/r3000@ecoff@sd.d: Remove test.
	* testsuite/gas/mips/r3900@ecoff@sd.d: Remove test.
	* testsuite/gas/mips/mips2@ecoff@sd.d: Remove test.
	* testsuite/gas/mips/mips32@ecoff@sd.d: Remove test.
	* testsuite/gas/mips/mips32r2@ecoff@sd.d: Remove test.
	* testsuite/gas/mips/mips1@ecoff@sd-forward.d: Remove test.
	* testsuite/gas/mips/r3000@ecoff@sd-forward.d: Remove test.
	* testsuite/gas/mips/r3900@ecoff@sd-forward.d: Remove test.
	* testsuite/gas/mips/mips2@ecoff@sd-forward.d: Remove test.
	* testsuite/gas/mips/mips32@ecoff@sd-forward.d: Remove test.
	* testsuite/gas/mips/mips32r2@ecoff@sd-forward.d: Remove test.