KABI: Add CONFIG_KABI_RESERVE to control KABI padding reserve

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I4K3S5

-----------------------

Add CONFIG_KABI_RESERVE to control KABI padding reserve or not,
for some embedded system, KABI padding reserve may be not necessary.

By the way, adjust unsigned long to u64 to unify basic reserve
length for both 32bit and 64bit architectures.
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>
Reviewed-by: NXie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

Kconfig

@@ -37,3 +37,11 @@ config KABI_SIZE_ALIGN_CHECKS
 	help
 	  This option enables more stringent kabi checks. Those must be disable
 	  in case of a debug-build because they allow to change struct sizes.
+
+config KABI_RESERVE
+	bool "Enable KABI PADDING RESERVE"
+	default y
+	help
+	  This option enables KABI padding reserve.
+	  For some embedded system, KABI padding reserve may be not necessary.
+	  Disable it on demand.

include/linux/kabi.h

@@ -425,7 +425,11 @@
  * leverage those common names making it easier to read and find in the
  * code.
  */
-# define _KABI_RESERVE(n)		unsigned long kabi_reserved##n
+#ifdef CONFIG_KABI_RESERVE
+	# define _KABI_RESERVE(n)		u64 kabi_reserved##n
+#else
+	# define _KABI_RESERVE(n)
+#endif
 # define KABI_RESERVE(n)		_KABI_RESERVE(n);
 /*
  * Simple wrappers to replace standard openEuler reserved elements.