Delete opcodes that have been removed from ISA 3.0.

opcodes/
	* ppc-opc.c <xscmpnedp>: Delete.
	<xvcmpnedp>: Likewise.
	<xvcmpnedp.>: Likewise.
	<xvcmpnesp>: Likewise.
	<xvcmpnesp.>: Likewise.

gas/
	* testsuite/gas/ppc/power9.d <xscmpnedp, xvcmpnedp, xvcmpnedp.,
	xvcmpnesp, xvcmpnesp.>: Delete tests.
	* testsuite/gas/ppc/power9.s: Likewise.
	* testsuite/gas/ppc/vsx3.d: Likewise.
	* testsuite/gas/ppc/vsx3.s: Likewise.