evas-drm: Fix evas drawing delay for cedric

evas-drm: Fix evas drawing delay for cedric

@bugfix: Draw to the front buffer first, instead of the back buffer.

Frenchie says this improves the "initial rendering delay" of expedite
tests. Originally, we were drawing to the back buffer first, then
flipping it onto the crtc when drawing was done. This presented a
"perceived" rendering delay when running expedite tests as it would
wait for the back buffer to be drawn before presenting it. Personally,
I think it is not good to draw directly to the front buffer first as
it may get presented "incomplete" ... but cedric says it draws fine so
we'll leave it starting on the front buffer (for now).

Signed-off-by: Chris Michael <devilhorns@comcast.net>