plotter: Missing metaclass declaration
plotter: Missing metaclass declaration

AbstractDataPlotter was missing abstract __metaclass__

Change-Id: Iaf59f6deaae218fcc76844149c9ba5fa7b5a4daf
Signed-off-by: Kapileshwar Singh <d373e2b6407ea84be359ce4a11e8631121819e79@arm.com>

sinkap/trappy,JaviMerino/trappy,bjackman/trappy,JaviMerino/trappy,joelagnel/trappy,ARM-software/trappy,sinkap/trappy,derkling/trappy,bjackman/trappy,bjackman/trappy,derkling/trappy,JaviMerino/trappy,ARM-software/trappy,bjackman/trappy,ARM-software/trappy,joelagnel/trappy,joelagnel/trappy,sinkap/trappy,derkling/trappy,sinkap/trappy,joelagnel/trappy,ARM-software/trappy