compiler_types.h: Move __nocfi out of compiler-specific header

Prepare for GCC KCFI support and move the __nocfi attribute from
compiler-clang.h to compiler_types.h. This was already gated by
CONFIG_CFI_CLANG, so this remains safe for non-KCFI GCC builds.

Signed-off-by: Kees Cook <[e-mail]>
Signed-off-by: Peter Zijlstra (Intel) <[e-mail]>
Reviewed-by: Nathan Chancellor <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

include/linux/compiler-clang.h

···
 # define __noscs	__attribute__((__no_sanitize__("shadow-call-stack")))
 #endif
 
-#if __has_feature(kcfi)
-/* Disable CFI checking inside a function. */
-#define __nocfi		__attribute__((__no_sanitize__("kcfi")))
-#endif
-
 /*
  * Turn individual warnings and errors on and off locally, depending
  * on version.

include/linux/compiler_types.h

···
 # define __noscs
 #endif
 
-#ifndef __nocfi
+#if defined(CONFIG_CFI_CLANG)
+# define __nocfi		__attribute__((__no_sanitize__("kcfi")))
+#else
 # define __nocfi
 #endif