ARM: OMAP2+: Fix smatch found issue for omap_device

The patch d85a2d61: "ARM: OMAP2+: Populate legacy resources for
dma and smartreflex" from Oct 10, 2017, leads to the following Smatch
complaint:

arch/arm/mach-omap2/omap_device.c:453 omap_device_copy_resources()
         error: we previously assumed 'oh' could be null (see line 394)

Fixes: d85a2d61: ("ARM: OMAP2+: Populate legacy resources for dma
and smartreflex")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>