doc: askenv: Reword and remove return value

With the addition of general text about how the return value is handled,
remove the examples from the askenv documentation as they are all normal
expected results.

Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Quentin Schulz <quentin.schulz@cherry.de>

doc/usage/cmd/askenv.rst

@@ -42,9 +42,8 @@ Value of a environment variable env1 without message and size parameters:
 
 ::
 
-    => askenv env1;echo $?
+    => askenv env1
     Please enter 'env1': val1
-    0
     => printenv env1
     env1=val1
 
@@ -52,9 +51,8 @@ Value of a environment variable env2 with message and size parameters:
 
 ::
 
-    => askenv env2 Please type-in a value for env2: 10;echo $?
+    => askenv env2 Please type-in a value for env2: 10
     Please type-in a value for env2: 1234567890123
-    0
     => printenv env2
     env2=1234567890
 
@@ -62,31 +60,12 @@ Value of a environment variable env3 with size parameter only:
 
 ::
 
-    => askenv env3 10;echo $?
+    => askenv env3 10
     Please enter 'env3': val3
-    0
     => printenv env3
     env3=val3
 
-Return Value of askenv command, when used without any other arguments:
-
-::
-
-    => askenv;echo $?
-    askenv - get environment variables from stdin
-
-    Usage:
-    askenv name [message] [size]
-        - display 'message' and get environment variable 'name' from stdin (max 'size' chars)
-    1
-
 Configuration
 -------------
 
 The askenv command is only available if CMD_ASKENV=y
-
-Return value
-------------
-
-The return value $? is set to 0 (true).
-If no other arguments are specified (along with askenv), it is set to 1 (false).