usb: typec: tcpm: Address incorrect values of tcpm psy for fixed supply

tcpm_pd_build_request overwrites current_limit and supply_voltage
even before port partner accepts the requests. This leaves stale
values in current_limit and supply_voltage that get exported by
"tcpm-source-psy-". Solving this problem by caching the request
values of current limit/supply voltage in req_current_limit
and req_supply_voltage. current_limit/supply_voltage gets updated
once the port partner accepts the request.

Fixes: f2a8aa05

 ("typec: tcpm: Represent source supply through power_supply")
Signed-off-by: Badhri Jagan Sridharan <badhri@google.com>
Cc: stable <stable@vger.kernel.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Adam Thomson <Adam.Thomson.Opensource@diasemi.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://lore.kernel.org/r/20210407200723.1914388-1-badhri@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>