google-material-design-icons: new package

[Thomas: simplify condition on
$(BR2_PACKAGE_GOOGLE_MATERIAL_DESIGN_ICONS_TYPE_PNG) and
$(BR2_PACKAGE_GOOGLE_MATERIAL_DESIGN_ICONS_TYPE_SVG).]

Signed-off-by: James Knight <james.d.knight@live.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>