usb: chipidea: core: Fix incorrectly documented function 'ci_usb_phy_exit()'

usb: chipidea: core: Fix incorrectly documented function 'ci_usb_phy_exit()'

Fixes the following W=1 kernel build warning(s):

 drivers/usb/chipidea/core.c:343: warning: expecting prototype for _ci_usb_phy_exit(). Prototype was for ci_usb_phy_exit() instead

Cc: Peter Chen <peter.chen@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Liam Girdwood <lgirdwood@gmail.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: David Lopo <dlopo@chipidea.mips.com>
Cc: linux-usb@vger.kernel.org
Acked-by: Peter Chen <peter.chen@kernel.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20210526130037.856068-14-lee.jones@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>