MIPS/GAS/testsuite: Reenable disabled external BEQ tests

MIPS/GAS/testsuite: Reenable disabled external BEQ tests

Complement:

commit bad36eacdad37042c4efb1c5fbf48476b47de82b
Author: Daniel Jacobowitz <drow@false.org>
Date:   Wed Nov 23 14:04:18 2005 +0000

<https://sourceware.org/ml/binutils/2005-11/msg00324.html>,
("R_MIPS_PC16, again"), and reenable external BEQ tests, the remaining
subset missed from the set of branch tests previously disabled with:

commit 6f171daac941741e5fa904f6e462adb75a595495
Author: Alexandre Oliva <aoliva@redhat.com>
Date:   Thu Dec 12 04:40:22 2002 +0000

<https://sourceware.org/ml/binutils/2002-11/msg00631.html>, ("mips:
branches to external labels are broken").

	gas/
	* testsuite/gas/mips/beq.s: Uncomment branches to undefined
	symbols.
	* testsuite/gas/mips/beq.d: Update accordingly.
	* testsuite/gas/mips/mipsr6@beq.d: Likewise.
	* testsuite/gas/mips/micromips@beq.d: Likewise.