gallium/targets: fix bool setting on BE architectures

gallium/targets: fix bool setting on BE architectures

val_bool and val_int are in a union. val_bool gets the first byte, which
happens to work on LE when setting via the int, but breaks on BE. By
setting the value properly, we are able to use DRI3 on BE architectures.
Tested by running glxgears with a NV34 in a G5 PPC.

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Cc: mesa-stable@lists.freedesktop.org
[Emil Velikov: squash the vmwgfx hunk]
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
(cherry picked from commit 6af14778a3f68030c4ad6426c75fe25d726235d5)