usb: dwc2: Add exit clock gating from session request interrupt

Added clock gating exit flow from session
request interrupt handler according programming guide.

Signed-off-by: Artur Petrosyan <Arthur.Petrosyan@synopsys.com>
Link: https://lore.kernel.org/r/20210413073638.921E8A0099@mailhost.synopsys.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>