usb: fotg210-udc: fix function kernel-doc comments

Correct kernel-doc comments to prevent warnings from
scripts/kernel-doc.

fotg210-udc.c:1103: warning: Function parameter or member 'g' not described in 'fotg210_vbus_session'
fotg210-udc.c:1103: warning: Excess function parameter '_gadget' description in 'fotg210_vbus_session'
fotg210-udc.c:1103: warning: No description found for return value of 'fotg210_vbus_session'
fotg210-udc.c:1129: warning: No description found for return value of 'fotg210_phy_event'

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc:  <linux-usb@vger.kernel.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20231206181335.27540-1-rdunlap@infradead.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>