cbgfx: allow draw_bitmap to render outside canvas

cbgfx: allow draw_bitmap to render outside canvas

This change allows draw_bitmap to draw an image outside the canvas
with the original size if the scale parameter is zero. This is used
for example when drawing a splash screen which has to be positioned
at a pixel perfect location.

BUG=none
BRANCH=master
TEST=Draw pictures and boxes on Samus and Ryu

Change-Id: Ia2d8799184d1aa192e2c50850e248bee8f234006
Signed-off-by: Patrick Georgi <pgeorgi@google.com>
Original-Commit-Id: 45d4717fe5c3e3554bd79b63ade490d88cf00bbe
Original-Change-Id: I48aa21122cfc2ee43bcb1b8f87b00c66abdc230e
Original-Signed-off-by: Daisuke Nojiri <dnojiri@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/295961
Original-Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/11923
Tested-by: build bot (Jenkins)