arm64/cpufeature: Introduce ID_PFR2 CPU register

This adds basic building blocks required for ID_PFR2 CPU register which
provides information about the AArch32 programmers model which must be
interpreted along with ID_PFR0 and ID_PFR1 CPU registers. This is added
per ARM DDI 0487F.a specification.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: kvmarm@lists.cs.columbia.edu
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org

Suggested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/1589881254-10082-5-git-send-email-anshuman.khandual@arm.com


Signed-off-by: Will Deacon <will@kernel.org>