tile: use free_bootmem_late() for initrd

commit 3f81d2447b37ac697b3c600039f2c6b628c06e21 upstream.

We were previously using free_bootmem() and just getting lucky
that nothing too bad happened.

Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>