PPC sync instruction accepts invalid and incompatible operands

PPC sync instruction accepts invalid and incompatible operands

ISA 2.07 added a new category called Elemental Memory Barriers that modifies
the sync instruction to accept an additional operand ESYNC.  Edmar added
support for this insruction varient here:

    https://sourceware.org/ml/binutils/2012-02/msg00221.html

Looking at this closer, I see that the insert_ls() function is misnamed
(since it's attached to the ESYNC operand, not the LS operand) but more
importantly, it is silently modifying the LS operand value behind the
users back when the LS operand is either invalid or is incompatible with
the new ESYNC operand.  The ISA 2.07 doc has an Assembler Note that clearly
states that assemblers that support the ESYNC operand should report all
invalid uses of LS and ESYNC.  This patch changes the assembler to
error out on invalid and incompatible operand usage.

opcodes/
	* ppc-opc.c (insert_ls): Test for invalid LS operands.
	(insert_esync): New function.
	(LS, WC): Use insert_ls.
	(ESYNC): Use insert_esync.

gas/testsuite/
	* gas/ppc/e6500.s <sync>: Fix invalid test.
	* gas/ppc/e6500.d: Likewise.