Remove E6500 insns from PPC_OPCODE_ALTIVEC2

Remove E6500 insns from PPC_OPCODE_ALTIVEC2

This isn't losing anything from the testsuite.  All of these insns
appear in testsuite/gas/ppc/e6500.s

opcodes/
	* ppc-opc.c (powerpc_opcodes <mviwsplt, mvidsplt, lvexbx, lvepxl,
	lvexhx, lvepx, lvexwx, stvexbx, stvexhx, stvexwx, lvtrx, lvtlx,
	lvswx, stvfrx, stvflx, stvswx, lvsm, stvepxl, lvtrxl, stvepx,
	lvtlxl, lvswxl, stvfrxl, stvflxl, stvswxl>): Enable E6500 only
	vector instructions with E6500 not PPCVEC2.
gas/
	* testsuite/gas/ppc/altivec2.s: Delete E6500 vector insns.
	* testsuite/gas/ppc/altivec2.d: Adjust to suit.