arm64/sysreg: Add register fields for HFGWTR2_EL2

This adds register fields for HFGWTR2_EL2 as per the definitions based
on DDI0601 2024-09.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Mark Brown <broonie@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>