usb: gadget: tegra: fix kernel panic in test mode

usb: gadget: tegra: fix kernel panic in test mode

Drivers should NOT use virt_to_phys,
use dma_map_single instead.

Bug 200098808

Change-Id: If5aacd97fb24d33860bf52ce42e3c56cd39c4762
Signed-off-by: BH Hsieh <bhsieh@nvidia.com>
Reviewed-on: http://git-master/r/761735
Reviewed-by: ChihMin Cheng <ccheng@nvidia.com>
Reviewed-by: Ashutosh Jha <ajha@nvidia.com>
Reviewed-on: http://git-master/r/1157107
Reviewed-by: Rohith Seelaboyina <rseelaboyina@nvidia.com>
Tested-by: Rohith Seelaboyina <rseelaboyina@nvidia.com>
Reviewed-by: Rakesh Babu Bodla <rbodla@nvidia.com>