use arm arch to detect rp2040

hw/bsp/rp2040/family.c

@@ -80,9 +80,9 @@ bool __no_inline_not_in_flash_func(get_bootsel_button)(void) {
   // The HI GPIO registers in SIO can observe and control the 6 QSPI pins.
   // Note the button pulls the pin *low* when pressed.
 
-  #if PICO_RP2040
+  #ifdef __ARM_ARCH_6M__ // CM0 for rp2040
     #define CS_BIT (1u << 1)
-  #else
+  #else // rp2350 (cm33/risv)
     #define CS_BIT SIO_GPIO_HI_IN_QSPI_CSN_BITS
   #endif
   bool button_state = (sio_hw->gpio_hi_in & CS_BIT);