tools: ynl: create local ARRAY_SIZE() helper

libc doesn't have an ARRAY_SIZE() create one locally.

Acked-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Link: https://lore.kernel.org/r/20240227223032.1835527-6-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

tools/net/ynl/lib/ynl-priv.h

@@ -27,6 +27,9 @@ enum ynl_policy_type {
 	YNL_PT_BITFIELD32,
 };
 
+#define YNL_ARRAY_SIZE(array)	(sizeof(array) ?			\
+				 sizeof(array) / sizeof(array[0]) : 0)
+
 struct ynl_policy_attr {
 	enum ynl_policy_type type;
 	unsigned int len;