usb: dwc2: host: always increment available host channel during release

When releasing a channel, increment hsotg->available_host_channels even
in case a periodic channel is released.

Acked-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Gregory Herrero <gregory.herrero@intel.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>