arm64/sysreg: Update ID_AA64ISAR2_EL1 description to DDI0601 2025-12

The 2025 extensions update the LUT field for new instructions added by
SVE and SME 2.3, there is no separate FEAT_ feature for these.

Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Author: broonie

arch/arm64/tools/sysreg

@@ -1978,6 +1978,7 @@ EndEnum
 UnsignedEnum	59:56	LUT
 	0b0000	NI
 	0b0001	IMP
+	0b0010	LUT6
 EndEnum
 UnsignedEnum	55:52	CSSC
 	0b0000	NI