shell: Add 'reset' command to reset the card

At some points during an interactive session or a script one may want
to reset the card.

Change-Id: I992eb3e0ed52f7941a5fb44f28a42e22ebd49301
diff --git a/docs/shell.rst b/docs/shell.rst
index 5170999..08fd376 100644
--- a/docs/shell.rst
+++ b/docs/shell.rst
@@ -193,6 +193,12 @@
 FIXME
 
 
+reset
+~~~~~
+
+Perform card reset and display the card ATR.
+
+
 Linear Fixed EF commands
 ------------------------