arm64: cpufeature: Add HAFT to cpucap_is_possible()

arm64: cpufeature: Add HAFT to cpucap_is_possible()

For consistency with other cpucaps, handle the configuration check for
ARM64_HAFT in cpucap_is_possible() rather than this being explicit in
system_supports_haft(). The configuration check will now happen
implicitly as cpus_have_final_cap() uses cpucap_is_possible() via
alternative_has_cap_unlikely().

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20241209155948.2124393-1-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>