Add the functionality for reading/writing pseudo registers.

On SVE the V registers are pseudo registers. This is supported
by adding AARCH64_SVE_V0_REGNUM.

	* aarch64-tdep.c (AARCH64_SVE_V0_REGNUM): Add define.
	(aarch64_vnv_type): Add function.
	(aarch64_pseudo_register_name): Add V regs for SVE.
	(aarch64_pseudo_register_type): Likewise.
	(aarch64_pseudo_register_reggroup_p): Likewise.
	(aarch64_pseudo_read_value_2): Use V0 offset for SVE
	(aarch64_pseudo_read_value): Add V regs for SVE.
	(aarch64_pseudo_write_2): Use V0 offset for SVE
	(aarch64_pseudo_write): Add V regs for SVE.
	* aarch64-tdep.h (struct gdbarch_tdep): Add vnv_type.