usb: dwc2: Add extra delay when forcing dr_mode

Fixes an issue found on rockchip rk3036 and rk3188 SOC platforms. For
some reason, the existing msleep(25) is not enough after the force mode.
The following patch was reported to fix the issue.

This does increase the probe delay again slightly, but not up to the
level it was before the original series of patches that this fixes. It
does not cause any other issues when tested on Synopsys HAPS and Altera
socfpga platforms.

Need to revisit this series next release to see if we can address these
issues without having an unconditional delay.

Fixes: 09c96980 ("usb: dwc2: Add functions to set and clear force mode")
Reported-by: Caesar Wang <caesar.upstream@gmail.com>
Reported-by: Michael Niewoehner <linux@mniewoehner.de>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Tested-by: Caesar Wang <caesar.upstream@gmail.com>
Signed-off-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>

drivers/usb/dwc2/core.c

@@ -619,6 +619,12 @@ void dwc2_force_dr_mode(struct dwc2_hsotg *hsotg)
 			 __func__, hsotg->dr_mode);
 		break;
 	}
+
+	/*
+	 * NOTE: This is required for some rockchip soc based
+	 * platforms.
+	 */
+	msleep(50);
 }
 
 /*