simplefb: Fix build failure on Sparc

of_platform_device_create is only defined when CONFIG_OF_ADDRESS is set,
which is normally always the case when CONFIG_OF is defined, except on Sparc,
so explicitly check for CONFIG_OF_ADDRESS rather then for CONFIG_OF.

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>