rp2/modrp2: Fix rp2.bootsel_button() function for RP2350.

Co-authored-by: graham sanderson <graham.sanderson@raspberrypi.com>
Signed-off-by: Phil Howard <github@gadgetoid.com>

ports/rp2/modrp2.c

@@ -42,11 +42,17 @@
 MP_DECLARE_CONST_FUN_OBJ_VAR_BETWEEN(mod_network_country_obj);
 #endif
 
+#define CS_PIN_INDEX 1
+
+#if PICO_RP2040
+#define CS_BIT (1u << CS_PIN_INDEX)
+#else
+#define CS_BIT SIO_GPIO_HI_IN_QSPI_CSN_BITS
+#endif
+
 // Improved version of
 // https://github.com/raspberrypi/pico-examples/blob/master/picoboard/button/button.c
 static bool __no_inline_not_in_flash_func(bootsel_button)(void) {
-    const uint CS_PIN_INDEX = 1;
-
     // Disable interrupts and the other core since they might be
     // executing code from flash and we are about to temporarily
     // disable flash access.
@@ -65,7 +71,7 @@ static bool __no_inline_not_in_flash_func(bootsel_button)(void) {
 
     // The HI GPIO registers in SIO can observe and control the 6 QSPI pins.
     // The button pulls the QSPI_SS pin *low* when pressed.
-    bool button_state = !(sio_hw->gpio_hi_in & (1 << CS_PIN_INDEX));
+    bool button_state = !(sio_hw->gpio_hi_in & CS_BIT);
 
     // Restore the QSPI_SS pin so we can use flash again.
     hw_write_masked(&ioqspi_hw->io[CS_PIN_INDEX].ctrl,