arm64: Use static keys for CPU features

arm64: Use static keys for CPU features

This patch adds static keys transparently for all the cpu_hwcaps
features by implementing an array of default-false static keys and
enabling them when detected. The cpus_have_cap() check uses the static
keys if the feature being checked is a constant, otherwise the compiler
generates the bitmap test.

Because of the early call to static_branch_enable() via
check_local_cpu_errata() -> update_cpu_capabilities(), the jump labels
are initialised in cpuinfo_store_boot_cpu().

Cc: Will Deacon <[email protected]>
Cc: Suzuki K. Poulose <[email protected]>
Signed-off-by: Catalin Marinas <[email protected]>
Signed-off-by: Will Deacon <[email protected]>