usb: dwc3: Decouple USB 2.0 L1 & L2 events

usb: dwc3: Decouple USB 2.0 L1 & L2 events

On DWC_usb3 revisions 3.00a and newer (including DWC_usb31 and
DWC_usb32) the GUCTL1 register gained the DEV_DECOUPLE_L1L2_EVT
field (bit 31) which when enabled allows the controller in device
mode to treat USB 2.0 L1 LPM & L2 events separately.

After commit 9bbf2165acdf ("usb: dwc3: gadget: Enable suspend
events") the controller will now receive events (and therefore
interrupts) for every state change when entering/exiting either
L1 or L2 states.  Since L1 is handled entirely by the hardware
and requires no software intervention, there is no need to even
enable these events and unnecessarily notify the gadget driver.
Enable the aforementioned bit to help reduce the overall interrupt
count for these L1 events that don't need to be handled while
retaining the events for full L2 suspend/wakeup.

Tested-by: Jun Li <jun.li@nxp.com>
Tested-by: Amit Pundir <amit.pundir@linaro.org> # for RB5 (sm8250)
Tested-by: John Stultz <john.stultz@linaro.org> # for HiKey960 & db845c
Reviewed-by: Jun Li <jun.li@nxp.com>
Acked-by: Felipe Balbi <balbi@kernel.org>
Signed-off-by: Jack Pham <jackp@codeaurora.org>
Link: https://lore.kernel.org/r/20210812082635.12924-1-jackp@codeaurora.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>