[X86] Remove 'opaque ptr' from the intel syntax parser and printer.

Previously for instructions like fxsave we would print "opaque ptr" as part of the memory operand. Now we print nothing.

We also no longer accept "opaque ptr" in the parser. We still accept any size to be specified for these instructions, but we may want to consider only parsing when no explicit size is specified. This what gas does.

llvm-svn: 331243