tools/pyboard.py: Make get_time use machine.RTC instead of pyb.RTC.

The current code evaluates `pyb.RTC().datetime()` resulting in a remote
side exception, as `pyb` is not defined on most ports (only stm32).

The code should evaluate `machine.RTC().datetime()` and hence return the
current time.

Signed-off-by: rufusclark <50201718+rufusclark@users.noreply.github.com>
Signed-off-by: Damien George <damien@micropython.org>

Author: rufusclark

tools/pyboard.py

@@ -506,7 +506,7 @@ def execfile(self, filename):
         return self.exec_(pyfile)
 
     def get_time(self):
-        t = str(self.eval("pyb.RTC().datetime()"), encoding="utf8")[1:-1].split(", ")
+        t = str(self.eval("machine.RTC().datetime()"), encoding="utf8")[1:-1].split(", ")
         return int(t[4]) * 3600 + int(t[5]) * 60 + int(t[6])
 
     def fs_exists(self, src):