mmc: omap_hsmmc: Skip platform_get_resource_byname() for dt case

MMC driver probe will abort for DT case because of failed
platform_get_resource_byname() lookup. Fix it by skipping resource
lookup byname for device tree build.

Issue is hidden because hwmod populates the IO resources which
helps to succeed platform_get_resource_byname() and probe.

Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: Balaji T K <balajitk@ti.com>
Signed-off-by: Chris Ball <cjb@laptop.org>