omp: Reorder call for TARGET_SIMD_CLONE_ADJUST

This patch moves the call to TARGET_SIMD_CLONE_ADJUST until after the arguments
and return types have been transformed into vector types.  It also constructs
the adjuments and retval modifications after this call, allowing targets to
alter the types of the arguments and return of the clone prior to the
modifications to the function definition.

gcc/ChangeLog:

	* omp-simd-clone.cc (simd_clone_adjust_return_type): Hoist out code to
	create return array and don't return new type.
	(simd_clone_adjust_argument_types): Hoist out code that creates
	ipa_param_body_adjustments and don't return them.
	(simd_clone_adjust): Call TARGET_SIMD_CLONE_ADJUST after return and
	argument types have been vectorized, create adjustments and return array
	after the hook.
	(expand_simd_clones): Call TARGET_SIMD_CLONE_ADJUST after return and
	argument types have been vectorized.