Disable IRQs on RP2040 during HW division

The divider is a shared HW resource, and when an IRQ comes in (i.e.
when a packet is processed by LWIP and the user's callbacks) its state can
be corrupted silently and randomly.

Change the Pico-SDK defaults to disable IRQs during division operations,
avoiding the issue by disallowing the LWIP callback to happen until after
division is completed.

Fixes #3212

Author: earlephilhower

lib/platform_def.txt

@@ -71,6 +71,7 @@
 -DPICO_USE_BLOCKED_RAM=0
 -DPICO_XOSC_STARTUP_DELAY_MULTIPLIER=64
 -DPICO_MAX_SHARED_IRQ_HANDLERS=6
+-DPICO_DIVIDER_DISABLE_INTERRUPTS=1
 
 -DPICO_CYW43_ARCH_HEADER=stdint.h
 -DCYW43_TASK_STACK_SIZE=1024