usb: dwc2: use a longer AHB idle timeout in dwc2_core_reset()

Use a 10000us AHB idle timeout in dwc2_core_reset() and make it
consistent with the other "wait for AHB master IDLE state" ocurrences.

This fixes a problem for me where dwc2 would not want to initialize when
updating to 4.19 on a MIPS Lantiq VRX200 SoC. dwc2 worked fine with
4.14.
Testing on my board shows that it takes 180us until AHB master IDLE
state is signalled. The very old vendor driver for this SoC (ifxhcd)
used a 1 second timeout.
Use the same timeout that is used everywhere when polling for
GRSTCTL_AHBIDLE instead of using a timeout that "works for one board"
(180us in my case) to have consistent behavior across the dwc2 driver.

Cc: linux-stable <stable@vger.kernel.org> # 4.19+
Acked-by: Minas Harutyunyan <hminas@synopsys.com>
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>