Register PixelArea property only if required.

Register PixelArea property only if required.

Since we were try to register uPixelArea property for every image-visual,
The Shader try to send PropertResetter very frequencly.

Since we only need to register that property only 1 time +
We can control pixel area by Renderer,
Let we register uPixelArea property only 1 times for creation.

And also, there was some useless uPixelArea usage on text-visual.
Let we just remove it.

Change-Id: Ib784e0088243f2a70f8556ae0dc9fa7c957b5aa2
Signed-off-by: Eunki, Hong <eunkiki.hong@samsung.com>