Fixes hanging on sleep_ms() after deep sleep

As documented in this repo for example: https://github.com/ghubcoder/PicoSleepDemo

src/rp2_common/pico_sleep/sleep.c

@@ -107,18 +107,27 @@ void sleep_goto_sleep_until(datetime_t *t, rtc_callback_t callback) {
     // We should have already called the sleep_run_from_dormant_source function
     assert(dormant_source_valid(_dormant_source));
 
+    // Save these register states to be able to restore afer waking up:
+    uint clock0_orig = clocks_hw->sleep_en0;
+    uint clock1_orig = clocks_hw->sleep_en1;
+    uint save = scb_hw->scr;
+
     // Turn off all clocks when in sleep mode except for RTC
     clocks_hw->sleep_en0 = CLOCKS_SLEEP_EN0_CLK_RTC_RTC_BITS;
     clocks_hw->sleep_en1 = 0x0;
 
     rtc_set_alarm(t, callback);
 
-    uint save = scb_hw->scr;
     // Enable deep sleep at the proc
     scb_hw->scr = save | M0PLUS_SCR_SLEEPDEEP_BITS;
 
     // Go to sleep
     __wfi();
+
+    // If these registers are not restored, any __wfi() will take the proc to deep sleep! (Any sleep_ms() for example.)
+    clocks_hw->sleep_en0 = clock0_orig;
+    clocks_hw->sleep_en1 = clock1_orig;
+    scb_hw->scr = save;
 }
 
 static void _go_dormant(void) {