arch: hexagon: include: uapi: asm: setup.h add swith macro __KERNEL__

Define dummy '__init' instead of include "linux/init.h" if !__KERNEL__,
or can not pass checking. The related error (with allmodconfig under
hexagon):

    CHECK   include/asm (34 files)
  usr/include/asm/setup.h:22: included file 'linux/init.h' is not exported
Signed-off-by: NChen Gang <gang.chen.5i5j@gmail.com>
Signed-off-by: NRichard Kuo <rkuo@codeaurora.org>

arch/hexagon/include/uapi/asm/setup.h

@@ -19,7 +19,12 @@
 #ifndef _ASM_SETUP_H
 #define _ASM_SETUP_H
 
+#ifdef __KERNEL__
 #include <linux/init.h>
+#else
+#define __init
+#endif
+
 #include <asm-generic/setup.h>
 
 extern char external_cmdline_buffer;