Add missing platform_set_drvdata() in omap_otg_probe(), otherwise
calling platform_get_drvdata() in remove returns NULL.

This is detected by Coccinelle semantic patch.
Signed-off-by: NWei Yongjun <weiyj.lk@gmail.com>
Signed-off-by: NFelipe Balbi <felipe.balbi@linux.intel.com>