targets/dri-vmwgfx: Convert to static/shared pipe-drivers

targets/dri-vmwgfx: Convert to static/shared pipe-drivers

Convert the final hardware driver to a single dri provider which
includes all the pipe-drivers.

Update the scons build and drop the unused vmw_powf.c.

Cc: José Fonseca <jfonseca@vmware.com>
Cc: Brian Paul <brianp@vmware.com>
Cc: Jakob Bornecrantz <jakob@vmware.com>
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Tested-by: Rob Clark <robclark@freedesktop.org>
Tested-by: Thomas Helland <thomashelland90 at gmail.com>
Acked-by: Tom Stellard <thomas.stellard@amd.com>