mfd: omap-usb-host: Provide description for 'pdev' argument to .probe()

Kerneldoc syntax is used, but not complete.  Arg descriptions required.

Prevents warnings like:

 drivers/mfd/omap-usb-host.c:531: warning: Function parameter or member 'pdev' not described in 'usbhs_omap_probe'

Cc: Tony Lindgren <tony@atomide.com>
Cc: Keshava Munegowda <keshava_mgowda@ti.com>
Cc: Roger Quadros <rogerq@ti.com>
Cc: linux-omap@vger.kernel.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/mfd/omap-usb-host.c

@@ -526,6 +526,8 @@ static const struct of_device_id usbhs_child_match_table[] = {
  * usbhs_omap_probe - initialize TI-based HCDs
  *
  * Allocates basic resources for this USB host controller.
+ *
+ * @pdev: Pointer to this device's platform device structure
  */
 static int usbhs_omap_probe(struct platform_device *pdev)
 {