usb: xhci-dwc3: Fix support for dis_enblslpm_quirk

No device tree in U-Boot or linux use the wrong spelling used in code.

Use correct property name as defined in dwc3 bindings.

Fixes: 062790f4 ("usb: xhci-dwc3: Add USB2 PHY configuration")
Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Reviewed-by: Marek Vasut <marex@denx.de>