arm64: cpufeature: add HWCAP for FEAT_RPRES

arm64: cpufeature: add HWCAP for FEAT_RPRES

commit 1175011a7d0030d49dc9c10bde36f08f26d0a8ee upstream.

Add a new HWCAP to detect the Increased precision of Reciprocal Estimate
and Reciprocal Square Root Estimate feature (FEAT_RPRES), introduced in Armv8.7.

Also expose this to userspace in the ID_AA64ISAR2_EL1 feature register.

Signed-off-by: Joey Gouly <joey.gouly@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Acked-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211210165432.8106-4-joey.gouly@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>