arm64: Implement cache_line_size() based on CTR_EL0.CWG

The hardware provides the maximum cache line size in the system via the
CTR_EL0.CWG bits. This patch implements the cache_line_size() function
to read such information, together with a sanity check if the statically
defined L1_CACHE_BYTES is smaller than the hardware value.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index e759af5d..9a5b5fe 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -242,6 +242,9 @@
 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
 	def_bool y
 
+config ARCH_HAS_CACHE_LINE_SIZE
+	def_bool y
+
 source "mm/Kconfig"
 
 config XEN_DOM0