PFW: Max value on bit parameters

BZ: 15708

Added Max attribute on bit parameter types.
Max attribute, as the parameter itself is unsigned and can't exceed the
maximum encodable value decided by the parameter's bit size.

In addition, fixed a small mistake in CParameterMgr::createParameterHandle
where now NULL is properly returned in case of failure instead of "false".

Change-Id: Ifb0af6b4d43dc2c0ddb4e0e038b1ce226772d71f
Signed-off-by: Patrick Benavoli <patrickx.benavoli@intel.com>
Reviewed-on: http://android.intel.com:8080/26098
Reviewed-by: Barthes, FabienX <fabienx.barthes@intel.com>
Tested-by: Barthes, FabienX <fabienx.barthes@intel.com>
Reviewed-by: buildbot <buildbot@intel.com>
Tested-by: buildbot <buildbot@intel.com>
diff --git a/parameter/ParameterMgr.cpp b/parameter/ParameterMgr.cpp
index f1dd9eb..66c8d9e 100644
--- a/parameter/ParameterMgr.cpp
+++ b/parameter/ParameterMgr.cpp
@@ -620,7 +620,7 @@
     // Nagivate through system class
     if (!pathNavigator.navigateThrough(getConstSystemClass()->getName(), strError)) {
 
-        return false;
+        return NULL;
     }
 
     // Find element
@@ -630,7 +630,7 @@
 
         strError = "Path not found";
 
-        return false;
+        return NULL;
     }
 
     // Check found element is a parameter
@@ -641,7 +641,7 @@
         // Element is not parameter
         strError = "Not a parameter";
 
-        return false;
+        return NULL;
     }
 
     // Convert as parameter and return new handle