HSI: omap_ssi: fix removal of port platform device

This avoids removal of the HSI port device when
only the platform port device should be removed
and clears the POPULATED bit in the DT node, so
that a new platform device is created when the
driver is probed again.

Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Sebastian Reichel <sre@kernel.org>