usb: typec: tcpm: turn tcpm_ams_finish into void function

usb: typec: tcpm: turn tcpm_ams_finish into void function

This function always return '0' and no callers use the return value.
So make it a void function.

This eliminates the following coccicheck warning:
./drivers/usb/typec/tcpm/tcpm.c:778:5-8: Unneeded variable: "ret".
Return "0" on line 794

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Link: https://lore.kernel.org/r/1615185330-118246-1-git-send-email-yang.lee@linux.alibaba.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>