trivial: fix an -> a typos in documentation and comments

It is always "an" if there is a vowel _spoken_ (not written).
So it is:
"an hour" (spoken vowel)
but
"a uniform" (spoken 'j')

Signed-off-by: Frederik Schwarzer <schwarzerf@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

include/linux/ncp_fs.h

@@ -87,7 +87,7 @@ struct ncp_objectname_ioctl
 #define NCP_AUTH_NDS	0x32
 	int		auth_type;
 	size_t		object_name_len;
-	void __user *	object_name;	/* an userspace data, in most cases user name */
+	void __user *	object_name;	/* a userspace data, in most cases user name */
 };
 
 struct ncp_privatedata_ioctl