MIPS/GAS/testsuite: Deduplicate error lists of branch local tests

Complement commit 7795a8f8 ("MIPS/GAS/testsuite: Convert branch
local list tests to dump tests") and share identical error lists among
branch local tests, removing duplicate copies.

	gas/
	* testsuite/gas/mips/branch-local-n32-2.d: Use `branch-local-2.l'
	for `error-output'.
	* testsuite/gas/mips/branch-local-n64-2.d: Likewise.
	* testsuite/gas/mips/branch-local-n32-3.d: Use `branch-local-3.l'
	for `error-output'.
	* testsuite/gas/mips/branch-local-n64-3.d: Likewise.
	* testsuite/gas/mips/branch-local-n32-2.l: Remove file.
	* testsuite/gas/mips/branch-local-n64-2.l: Remove file.
	* testsuite/gas/mips/branch-local-n32-3.l: Remove file.
	* testsuite/gas/mips/branch-local-n64-3.l: Remove file.