Add new mnemonics for VLE multiple load instructions

Add new mnemonics for VLE multiple load instructions

opcodes/
	* ppc-opc.c (vle_opcodes): Add e_lmvsprw, e_lmvgprw,
	e_lmvsrrw, e_lmvcsrrw and e_lmvcsrrw as official mnemonics for
	VLE multimple load/store instructions. Old e_ldm* variants are
	kept as aliases.
	Add missing e_lmvmcsrrw and e_stmvmcsrrw.
gas/
	* testsuite/gas/ppc/vle-mult-ld-st-insns.s: New file: Tests the
	support for the VLE multiple load/store instructions.
	* testsuite/gas/ppc/vle-mult-ld-st-insns.d: New file: Test
	driver.
	* testsuite/gas/ppc/ppc.exp: Run it.