ioapic.h: prevent potential compiler warning

Includes device.h to prevent potential compiler warnings due to use of
'struct device *' in _ioapic_init() declaration.

Change-Id: Iabd97c09385044a3742658f66a79be969b62852a
Work-by: Johan Kruger <johan.kruger@windriver.com>
Signed-off-by: Peter Mitsis <peter.mitsis@windriver.com>