Middle-end: Change order of LEN_MASK_LOAD/LEN_MASK_STORE arguments

Hi, Richard. I fix the order as you suggeted.

Before this patch, the order is {len,mask,bias}.

Now, after this patch, the order becomes {len,bias,mask}.

Since you said we should not need 'internal_fn_bias_index', the bias index should always be the len index + 1.
I notice LEN_STORE order is {len,vector,bias}, to make them consistent, I reorder into LEN_STORE {len,bias,vector}.
Just like MASK_STORE {mask,vector}.

Ok for trunk ?

gcc/ChangeLog:

	* config/riscv/autovec.md: Change order of
	LEN_MASK_LOAD/LEN_MASK_STORE/LEN_LOAD/LEN_STORE arguments.
	* config/riscv/riscv-v.cc (expand_load_store): Ditto.
	* doc/md.texi: Ditto.
	* gimple-fold.cc (gimple_fold_partial_load_store_mem_ref): Ditto.
	* internal-fn.cc (len_maskload_direct): Ditto.
	(len_maskstore_direct): Ditto.
	(add_len_and_mask_args): New function.
	(expand_partial_load_optab_fn): Change order of
	LEN_MASK_LOAD/LEN_MASK_STORE/LEN_LOAD/LEN_STORE arguments.
	(expand_partial_store_optab_fn): Ditto.
	(internal_fn_len_index): New function.
	(internal_fn_mask_index): Change order of
	LEN_MASK_LOAD/LEN_MASK_STORE/LEN_LOAD/LEN_STORE arguments.
	(internal_fn_stored_value_index): Ditto.
	(internal_len_load_store_bias): Ditto.
	* internal-fn.h (internal_fn_len_index): New function.
	* tree-ssa-dse.cc (initialize_ao_ref_for_dse): Change order of
	LEN_MASK_LOAD/LEN_MASK_STORE/LEN_LOAD/LEN_STORE arguments.
	* tree-vect-stmts.cc (vectorizable_store): Ditto.
	(vectorizable_load): Ditto.