forwprop: Manually rename the virtual mem op for complex and vector loads prop

forwprop: Manually rename the virtual mem op for complex and vector loads prop

There are two places which forwprop replaces an original load to a few different loads.
Both can set the vuse manually instead of relying on update_ssa.
One is doing a complex load followed by REAL/IMAG_PART only
And the other is very similar but for vector loads followed by BIT_FIELD_REF.

Since this was the last place that needed to handle updating the ssa form,
Remove the TODO_update_ssa also from the pass.

gcc/ChangeLog:

	* tree-ssa-forwprop.cc (optimize_vector_load): Set the vuse manually
	on the new load statements. Also remove forward declaration since
	the definition is before the first use.
	(pass_forwprop::execute): Likewise for complex loads.
	(pass_data_forwprop): Remove TODO_update_ssa.

Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>