linux/kconfig.h: replace IF_ENABLED() with PTR_IF() in <linux/kernel.h>

<linux/kconfig.h> is included from all the kernel-space source files,
including C, assembly, linker scripts. It is intended to contain a
minimal set of macros to evaluate CONFIG options.

IF_ENABLED() is an intruder here because (x ? y : z) is C code, which
should not be included from assembly files or linker scripts.

Also, <linux/kconfig.h> is no longer self-contained because NULL is
defined in <linux/stddef.h>.

Move IF_ENABLED() out to <linux/kernel.h> as PTR_IF(). PTF_IF()
takes the general boolean expression instead of a CONFIG option
so that it fits better in <linux/kernel.h>.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>

drivers/pinctrl/pinctrl-ingenic.c

@@ -11,6 +11,7 @@
 #include <linux/gpio/driver.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
+#include <linux/kernel.h>
 #include <linux/of_device.h>
 #include <linux/of_irq.h>
 #include <linux/of_platform.h>
@@ -3854,6 +3855,8 @@ static int __init ingenic_pinctrl_probe(struct platform_device *pdev)
 	return 0;
 }
 
+#define IF_ENABLED(cfg, ptr)	PTR_IF(IS_ENABLED(cfg), (ptr))
+
 static const struct of_device_id ingenic_pinctrl_of_match[] = {
 	{
 		.compatible = "ingenic,jz4730-pinctrl",

include/linux/kconfig.h

@@ -70,10 +70,4 @@
  */
 #define IS_ENABLED(option) __or(IS_BUILTIN(option), IS_MODULE(option))
 
-/*
- * IF_ENABLED(CONFIG_FOO, ptr) evaluates to (ptr) if CONFIG_FOO is set to 'y'
- * or 'm', NULL otherwise.
- */
-#define IF_ENABLED(option, ptr) (IS_ENABLED(option) ? (ptr) : NULL)
-
 #endif /* __LINUX_KCONFIG_H */

include/linux/kernel.h

@@ -48,6 +48,8 @@
  */
 #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]) + __must_be_array(arr))
 
+#define PTR_IF(cond, ptr)	((cond) ? (ptr) : NULL)
+
 #define u64_to_user_ptr(x) (		\
 {					\
 	typecheck(u64, (x));		\