exposay: delete outer padding from struct exposay_output

exposay: delete outer padding from struct exposay_output

After some changes in the exposay layout, the outer padding makes
no sense anymore. It was used to avoid the panel to get overlapped
by the exposay surfaces and to keep distance from the borders
of the window.

Currently, the exposay is centralized and the panel cannot get
overlapped. The outer padding just creates unnecessary unused
space, what makes exposay's surfaces smaller.

Delete outer padding from struct exposay_output.

Signed-off-by: Leandro Ribeiro <leandrohr@riseup.net>