usb: gadget: tegra: remove unnecessary bus resume

Current Tegra UDC driver share same IRQ with OTG driver, and it will call
bus_resume() even if there is no UDC IRQ pending.

This patch will check UDC IRQ source and will not cause bus resume if no
IRQ pending for UDC driver.

BUG 1015685

Change-Id: Ifc5634ae5d1f7f1435c64bc527ab2e9fb8d0e36b
Signed-off-by: Xin Xie <xxie@nvidia.com>
Reviewed-on: http://git-master/r/121896
Reviewed-by: Simone Willett <swillett@nvidia.com>
Tested-by: Simone Willett <swillett@nvidia.com>