mesa: don't set RCONFLICTS / PROVIDES if glvnd is enabled

mesa: don't set RCONFLICTS / PROVIDES if glvnd is enabled

If glvnd is enabled, mesa packages do not provide full library
implementations (instead it provides two ICDs, one for EGL, one for
GLX). This means that there is no more conflict between mesa packages
and other vendor packages. Stop setting those extra tags for mesa
packages.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>