zephyr test: Make ppc_discharge_vbus mockable
Allow tests to mock ppc_discharge_vbus. Support tests of discharging
behavior that are decoupled from the discharge indicator of a specific
PPC.
TEST=make buildall
BRANCH=none
@@ -200,8 +200,12 @@ int ppc_err_prints(const char *string, int port, int error);
* @param port: The Type-C port number.
* @param enable: 1 -> discharge vbus, 0 -> stop discharging vbus
* @return EC_SUCCESS on success, error otherwise.
+ *
+ * TODO(b/255413715): Remove test_mockable when it is practical to convert the
+ * usb_pd_flags test to use the unit-testing framework and not require weak
+ * functions for mocking.
*/
-int ppc_discharge_vbus(int port, int enable);
+test_mockable int ppc_discharge_vbus(int port, int enable);
/**
* Initializes the PPC for the specified port.
