device/root_device.c: Get rid of device_t

Use of `device_t` has been abandoned in ramstage.

Change-Id: Ia25c5097d4cfa979c18a855e656ad794c2f0260c
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/26008
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
1 file changed