drv/ioport_lpf2: set vcc pin to input on shutdown

There seem to still be issues with the some city hubs turning back on
when the power button is released.

This changes the gpio state for the I/O port VCC pin from out low to
input (floating) on shutdown. This seems to fix a similar issue
observed on the move hub as well, so we can drop the quirk for that
platform.

Fixes: pybricks/support#692

CHANGELOG.md

@@ -11,6 +11,11 @@
 - Indicate that the SPIKE Prime hub is booting and shutting down by fading
   the stop sign in and out.
 
+### Fixed
+- Fixed city hub turning back on after shutdown ([support#692]).
+
+[support#692]: https://github.com/pybricks/support/issues/692
+
 ## [3.2.0b3] - 2022-07-20
 
 ### Fixed

lib/pbio/drv/ioport/ioport_lpf2.c

@@ -459,14 +459,11 @@ PROCESS_THREAD(pbdrv_ioport_lpf2_process, ev, data) {
         // TODO: we need to ensure H-bridge power is off here to avoid potentially
         // damaging custom I/O devices.
 
-        #if PBDRV_CONFIG_IOPORT_LPF2_BOOST_SHUTDOWN_QUIRK
-        // The LEGO BOOST Move hub will turn right back on when the power button
-        // is released if we turn off VCC at shutdown for some reason (hardware bug?).
-        pbdrv_gpio_out_high(&pbdrv_ioport_lpf2_platform_data.port_vcc);
-        #else
         // Turn off power on pin 4 on all ports
-        pbdrv_gpio_out_low(&pbdrv_ioport_lpf2_platform_data.port_vcc);
-        #endif
+        // NB: there seems to be a hardware? issue on move/city hubs that if we
+        // set this to output low instead of input, the hub will turn back on
+        // as soon as the user releases the power button
+        pbdrv_gpio_input(&pbdrv_ioport_lpf2_platform_data.port_vcc);
 
         PROCESS_EXIT();
     });

lib/pbio/platform/move_hub/pbdrvconfig.h

@@ -40,7 +40,6 @@
 
 #define PBDRV_CONFIG_IOPORT                         (1)
 #define PBDRV_CONFIG_IOPORT_LPF2                    (1)
-#define PBDRV_CONFIG_IOPORT_LPF2_BOOST_SHUTDOWN_QUIRK (1)
 #define PBDRV_CONFIG_IOPORT_LPF2_NUM_PORTS          (2)
 #define PBDRV_CONFIG_IOPORT_LPF2_FIRST_PORT         PBIO_PORT_ID_C
 #define PBDRV_CONFIG_IOPORT_LPF2_LAST_PORT          PBIO_PORT_ID_D