vect: Remove type from misalignment hook.

vect: Remove type from misalignment hook.

This patch removes the type argument from the vector_misalignment hook.
Ever since we switched from element to byte misalignment its
semantics haven't been particularly clear and nowadays it should be
redundant.

Also, in case of gather/scatter, the patch sets misalignment to the
misalignment of one unit of the vector mode so targets can
distinguish between element size alignment and element mode alignment.

is_packed is now always set, regardless of misalignment.

gcc/ChangeLog:

	* config/aarch64/aarch64.cc (aarch64_builtin_support_vector_misalignment):
	Remove type.
	* config/arm/arm.cc (arm_builtin_support_vector_misalignment):
	Ditto.
	* config/epiphany/epiphany.cc (epiphany_support_vector_misalignment):
	Ditto.
	* config/gcn/gcn.cc (gcn_vectorize_support_vector_misalignment):
	Ditto.
	* config/loongarch/loongarch.cc (loongarch_builtin_support_vector_misalignment):
	Ditto.
	* config/riscv/riscv.cc (riscv_support_vector_misalignment):
	Ditto.
	* config/rs6000/rs6000.cc (rs6000_builtin_support_vector_misalignment):
	Ditto.
	* config/s390/s390.cc (s390_support_vector_misalignment):
	Ditto.
	* doc/tm.texi: Adjust vector misalignment docs.
	* target.def: Ditto.
	* targhooks.cc (default_builtin_support_vector_misalignment):
	Remove type.
	* targhooks.h (default_builtin_support_vector_misalignment):
	Ditto.
	* tree-vect-data-refs.cc (vect_can_force_dr_alignment_p):
	Set misalignment for gather/scatter and remove type.
	(vect_supportable_dr_alignment): Ditto.