re PR target/84264 (ICE in rs6000_emit_le_vsx_store, at config/rs6000/rs6000.c:10367 starting with r256656)

gcc/
	PR target/84264
	* config/rs6000/vector.md (mov<mode>): Disallow altivec memory operands.

gcc/testsuite/
	PR target/84264
	* g++.dg/pr84264.C: New test.

From-SVN: r258251