[AArch64] Fix lane specifier syntax

[AArch64] Fix lane specifier syntax

The syntax for lane specifiers uses a vector element rather than a vector:

fmls    v0.2s, v1.2s, v1.s[1]  // rather than v1.2s[1]

Fix all the lane specifiers to use Vetype which uses the correct element type.

    gcc/
	* aarch64/aarch64-simd.md (aarch64_mla_elt<mode>): Correct lane syntax.
	(aarch64_mla_elt_<vswap_width_name><mode>): Likewise.
	(aarch64_mls_elt<mode>): Likewise.
	(aarch64_mls_elt_<vswap_width_name><mode>): Likewise.
	(aarch64_fma4_elt<mode>): Likewise.
	(aarch64_fma4_elt_<vswap_width_name><mode>): Likewise.
	(aarch64_fma4_elt_to_64v2df): Likewise.
	(aarch64_fnma4_elt<mode>): Likewise.
	(aarch64_fnma4_elt_<vswap_width_name><mode>): Likewise.
	(aarch64_fnma4_elt_to_64v2df): Likewise.

    testsuite/
	* gcc.target/aarch64/fmla_intrinsic_1.c: Check for correct lane syntax.
	* gcc.target/aarch64/fmls_intrinsic_1.c: Likewise.
	* gcc.target/aarch64/mla_intrinsic_1.c: Likewise.
	* gcc.target/aarch64/mls_intrinsic_1.c: Likewise.