Tock V2 port - rebased and updated (#620)

* Changes from #580

* fixes USB cancel panic

* style fixes

* Update src/env/tock/storage.rs

Co-authored-by: Zach Halvorsen <zhalvorsen@google.com>

---------

Co-authored-by: Zach Halvorsen <zhalvorsen@google.com>

boards/nordic/nrf52840_mdk_dfu/src/io.rs

@@ -7,8 +7,7 @@ use kernel::hil::led;
 use kernel::hil::uart::{self, Configure};
 use nrf52840::gpio::Pin;
 
-use crate::CHIP;
-use crate::PROCESSES;
+use crate::{CHIP, PROCESSES, PROCESS_PRINTER};
 
 struct Writer {
     initialized: bool,
@@ -31,7 +30,7 @@ impl IoWrite for Writer {
         let uart = nrf52840::uart::Uarte::new();
         if !self.initialized {
             self.initialized = true;
-            uart.configure(uart::Parameters {
+            let _ = uart.configure(uart::Parameters {
                 baud_rate: 115200,
                 stop_bits: uart::StopBits::One,
                 parity: uart::Parity::None,
@@ -64,5 +63,6 @@ pub unsafe extern "C" fn panic_fmt(pi: &PanicInfo) -> ! {
         &cortexm4::support::nop,
         &PROCESSES,
         &CHIP,
+        &PROCESS_PRINTER,
     )
 }