drivers: base: cacheinfo: Add variable to record max cache line size

Add coherency_max_size variable to record the maximum cache line size
for different cache levels. If it is available, we will synchronize
it as cache line size, otherwise we will use CTR_EL0.CWG reporting
in cache_line_size() for arm64.

Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Jeremy Linton <jeremy.linton@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Shaokun Zhang <zhangshaokun@hisilicon.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

include/linux/cacheinfo.h

@@ -17,6 +17,8 @@ enum cache_type {
 	CACHE_TYPE_UNIFIED = BIT(2),
 };
 
+extern unsigned int coherency_max_size;
+
 /**
  * struct cacheinfo - represent a cache leaf node
  * @id: This cache's id. It is unique among caches with the same (type, level).