arm64: Add hwcaps for crypto and CRC32 extensions.

Advertise the optional cryptographic and CRC32 instructions to
user space where present. Several hwcap bits [3-7] are allocated.

Signed-off-by: Steve Capper <steve.capper@linaro.org>
[bit 2 is taken now so use bits 3-7 instead]
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>