Switch to unversioned Recommends and conditional
    
    This avoid a versioned Recommends, but keeps the effects so that same
    version of the mesa-va-drivers sub-package get enforced on mesa updates.
    
    Switching to Recommends instead of Requires was due to the fact that the
    package could be easily replaced.
    
    This commit fulfill this goal in practice
    
    Signed-off-by: Nicolas Chauvet <kwizart@gmail.com>