ksmbd: remove internal.h include

[ Upstream commit 211db0ac ]

Since vfs_path_lookup is exported, It should not be internal.
Move vfs_path_lookup prototype in internal.h to linux/namei.h.

Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Stable-dep-of: df9d70c1 ("cifs: if deferred close is disabled then close files immediately")
Signed-off-by: Sasha Levin <sashal@kernel.org>