Update "can deep sleep" function for LP ticker

When the define LPTICKER_DELAY_TICKS is set deep sleep can be randomly
disallowed when using the low power ticker. This is because a Timer
object, which locks deep sleep, is used to protect from back-to-back
writes to lp tickers which can't support that.

This patch updates the function sleep_manager_can_deep_sleep() to
return that deep sleep is allowed if only the lp ticker's Timeout
object is locking deep sleep. This allows tests which assert that
deep sleep should be allowed to pass.

Author: c1728p9

hal/mbed_sleep_manager.c

@@ -22,6 +22,7 @@
 #include "mbed_debug.h"
 #include "mbed_stats.h"
 #include "lp_ticker_api.h"
+#include "mbed_lp_ticker_wrapper.h"
 #include <limits.h>
 #include <stdio.h>
 #include "mbed_stats.h"
@@ -180,7 +181,13 @@ void sleep_manager_unlock_deep_sleep_internal(void)
 
 bool sleep_manager_can_deep_sleep(void)
 {
-    return deep_sleep_lock == 0 ? true : false;
+    uint32_t lock_count = deep_sleep_lock;
+#if DEVICE_LPTICKER && (LPTICKER_DELAY_TICKS > 0)
+    if (lp_ticker_get_timeout_pending() && (lock_count > 0)) {
+        lock_count--;
+    }
+#endif
+    return lock_count == 0 ? true : false;
 }
 
 void sleep_manager_sleep_auto(void)
@@ -196,7 +203,11 @@ void sleep_manager_sleep_auto(void)
 #ifdef MBED_DEBUG
     hal_sleep();
 #else
-    if (sleep_manager_can_deep_sleep()) {
+    if (sleep_manager_can_deep_sleep()
+#if DEVICE_LPTICKER && (LPTICKER_DELAY_TICKS > 0)
+        && !lp_ticker_get_timeout_pending()
+#endif
+    ) {
         deep = true;
         hal_deepsleep();
     } else {