arm64: cpufeature: Export this_cpu_has_cap helper

Export the this_cpu_has_cap() for use by modules. This is
used by TRBE driver. Without this patch, TRBE will fail
to build as a module :

ERROR: modpost: "this_cpu_has_cap" [drivers/hwtracing/coresight/coresight-trbe.ko] undefined!

Fixes: 8a106512

 ("coresight: trbe: Add infrastructure for Errata handling")
Cc: Will Deacon <will@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
[ change to EXPORT_SYMBOL_GPL ]
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
[ Added Will AB tag]
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20211103221256.725080-1-suzuki.poulose@arm.com
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>