vrend: Upload sysvalue data only if it has been changed since last use

Keep a cookie with the shader program to be able to check against the
sysvalue data cookie whether it has been touched, and upload the data
only then.

Signed-off-by: Gert Wollny <gert.wollny@collabora.com>
18 jobs for !893 with rework-sysval-buffer
merge request