During the conversion of this board to DM_REGULATOR, usb-mass-storage
was broken and started failing with the following error:
=> ums 0 mmc 2
UMS: LUN 0, dev 2, hwpart 0, sector 0x0, count 0xe90000
Error enabling VBUS supply
g_dnl_register: failed!, error: -38
g_dnl_register failed
Fix this by adding the relevant GPIO to the regulator node.
Fixes: 4ca99fe81a ("ARM: imx: dh-imx6: Enable DM regulator")
Signed-off-by: Harald Seiler <hws@denx.de>