sys/file.h: Allow inclusion when compiling for a strict namespace

Although not part of the standard, this file is sometimes included with
-D_POSIX_C_SOURCE=<value> or -D_XOPEN_SOURCE=<value>. Limit those
sturctures that use types hidden by __BSD_VISIBLE to when they are
visible.

PR:			259975, 234205
Sponsored by:		Netflix

sys/sys/file.h

@@ -174,6 +174,7 @@ struct fileops {
  * none	not locked
  */
 
+#if __BSD_VISIBLE
 struct fadvise_info {
 	int		fa_advice;	/* (f) FADV_* type. */
 	off_t		fa_start;	/* (f) Region start. */
@@ -213,12 +214,14 @@ struct file {
 
 #define	FOFFSET_LOCKED       0x1
 #define	FOFFSET_LOCK_WAITING 0x2
+#endif /* __BSD_VISIBLE */
 
 #endif /* _KERNEL || _WANT_FILE */
 
 /*
  * Userland version of struct file, for sysctl
  */
+#if __BSD_VISIBLE
 struct xfile {
 	ksize_t	xf_size;	/* size of struct xfile */
 	pid_t	xf_pid;		/* owning process */
@@ -238,6 +241,7 @@ struct xfile {
 	int	_xf_int_pad3;
 	int64_t	_xf_int64_pad[6];
 };
+#endif /* __BSD_VISIBLE */
 
 #ifdef _KERNEL