power-icon theming: Remove stray MnbToolbarButton theming.
power-icon theming: Remove stray MnbToolbarButton theming.

Fixes: BMC#266 -- Stray definitions of MnbToolbarButton base style in css

meego-netbook-ux/meego-panel-devices,meego-netbook-ux/meego-panel-devices,meego-netbook-ux/meego-panel-devices