gallium/pipebuffer: Add a cache buffer manager bypass mask

gallium/pipebuffer: Add a cache buffer manager bypass mask

In some situations, it may be desirable to bypass the cache at buffer
creation but to insert the buffer in the cache at buffer destruction.
One such situation is where we already have a kernel representation of a
buffer that we want to use, but we also want to insert it in the cache when
it's freed up.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: José Fonseca <jfonseca@vmware.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
Cc: "10.1" <mesa-stable@lists.freedesktop.org>