UPSTREAM: usb: dwc2: gadget: Add dwc2_gadget_read_ep_interrupts function

UPSTREAM: usb: dwc2: gadget: Add dwc2_gadget_read_ep_interrupts function

Reads and returns interrupts for given endpoint, by masking epint_reg
with corresponding mask.

Change-Id: I8f5af249b8569a19435665bef2c2a841672f1c03
Tested-by: John Keeping <john@metanate.com>
Signed-off-by: Vardan Mikayelyan <mvardan@synopsys.com>
Signed-off-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Huang, Tao <huangtao@rock-chips.com>
(cherry picked from commit 326015887b6a1321fd61f7a16816241ad841a03c)