[ARM] 3391/1: use PLAT8250_DEV_PLATFORM{,1} for platform device id instead of 0/1

Patch from Lennert Buytenhek

This patch changes iop3xx and omap2 and to use PLAT8250_DEV_PLATFORM{,1}
as platform device id instead of just hardcoding 0/1 directly.

Signed-off-by: Lennert Buytenhek <buytenh@wantstofly.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>