Use cyw43_delay_ms() in cyw43_spi_reset() instead of sleep_ms() (#2431)

Since cyw43_spi_reset() may be executed from an async context, we
should use cyw43_delay_ms() instead of sleep_ms(). This is particularly
a problem when using the async_context_threadsafe_background backend,
because sleep_ms() will assert in an ISR.

Author: mbrase

src/rp2_common/pico_cyw43_driver/cyw43_bus_pio_spi.c

@@ -359,9 +359,9 @@ void cyw43_spi_gpio_setup(void) {
 // Reset wifi chip
 void cyw43_spi_reset(void) {
     gpio_put(CYW43_PIN_WL_REG_ON, false); // off
-    sleep_ms(20);
+    cyw43_delay_ms(20);
     gpio_put(CYW43_PIN_WL_REG_ON, true); // on
-    sleep_ms(250);
+    cyw43_delay_ms(250);
 
     // Setup IRQ (24) - also used for DO, DI
     gpio_init(CYW43_PIN_WL_HOST_WAKE);