matrix-test: fix units in report
matrix-test: fix units in report

The matrix-test speed tests are calculated in ns but some printed the
units as us

Reviewed-by: Pekka Paalanen <0f6ae7001e34c37b02fb2c1c2573ddf8f442136a@collabora.co.uk>

Gnurou/weston,Tarnyko/weston-xdg_surface_present,sir-murray/weston,jonnylamb/weston,eyolfson/weston,krezovic/weston,eyolfson/weston,Tarnyko/weston-xdg_surface_present,Fantu/compositor-spice,Fantu/compositor-spice,sir-murray/weston,jonnylamb/weston,udoprog/weston,giucam/weston,mchalupa/weston,mchalupa/weston,Fantu/compositor-spice,kwm81/weston,krezovic/weston,kwm81/weston,xorgy/weston,giucam/weston,Gnurou/weston,udoprog/weston,xorgy/weston