ntfs3: rework xattr handlers and switch to POSIX ACL VFS helpers

The xattr code in ntfs3 is currently a bit confused. For example, it
defines a POSIX ACL i_op->set_acl() method but instead of relying on the
generic POSIX ACL VFS helpers it defines its own set of xattr helpers
with the consequence that i_op->set_acl() is currently dead code.

Switch ntfs3 to rely on the VFS POSIX ACL xattr handlers. Also remove
i_op->{g,s}et_acl() methods from symlink inode operations. Symlinks
don't support xattrs.

This is a preliminary change for the following patches which move
handling idmapped mounts directly in posix_acl_xattr_set().

This survives POSIX ACL xfstests.

Fixes: be71b5cb ("fs/ntfs3: Add attrib operations")
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Reviewed-by: Seth Forshee (DigitalOcean) <sforshee@kernel.org&gt;>