mx7dsabresd: Make 'ums' command functional

When running the 'ums' command we get:

=> ums 0 mmc 0
UMS: disk start sector: 0x0, count: 0xe18000
g_dnl_register: failed!, error: -22
ERROR: g_dnl_register failed
at common/cmd_usb_mass_storage.c:107/do_usb_mass_storage()

Fix this by initializing USB OTG1 port as USB device mode instead of host.

Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>