lrdp-v2: register.py: add doctest for single-bit fields

The Register class supports single-bit field definitions. Add a doctest
for example purposes and regression testing.

Change-Id: Ib04762aca8cb00256e16c29ac2ab71d47d0c06da

linux-ramdump-parser-v2/register.py

@@ -39,6 +39,14 @@ class Register(object):
     >>> abc.other = 0x3
     >>> hex(abc.value)
     '0x31'
+    >>> abc.add_field("just_a_bit", (4, 4))
+    >>> abc.just_a_bit
+    1
+    >>> abc.just_a_bit = 0
+    >>> abc.just_a_bit
+    0
+    >>> hex(abc.value)
+    '0x21'
     >>> abc.value = 0
     >>> abc.value
     0