targets/radeonsi/vdpau: convert to static/shared pipe-drivers

targets/radeonsi/vdpau: convert to static/shared pipe-drivers

Similar to previous commits, this allows us to minimise some
of the duplication by compacting all vdpau targets into a
single library.

v2: Include the radeon winsys only when there is a user for it.
v3: Correcly include the winsys. Now with extra brown bag :\

Cc: Christian König <christian.koenig@amd.com>
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Tested-by: Thomas Helland <thomashelland90 at gmail.com>