[ARM][trivial] Use uppercase for code iterator names

[ARM][trivial] Use uppercase for code iterator names

	* config/arm/iterators.md (shiftable_ops): Rename to...
	(SHIFTABLE_OPS): ... This.  Update use in comments.
	(ior_xor): Rename to...
	(IOR_XOR): ... This.
	(vqh_ops): Rename to...
	(VQH_OPS): ... This.
	(vqhs_ops): Rename to...
	(VQHS_OPS): ... This.
	(rshifts): Rename to...
	(RSHIFTS): ... This.
	(returns): Rename to...
	(RETURNS): ... This.
	* config/arm/arm.md: Update uses of the above.
	* config/arm/neon.md: Likewise.

From-SVN: r222416