radv: fix missing initialization of the conditional rendering state

This was missing when VK_EXT_conditional_rendering has been
implemented. The predication type should be -1 to avoid
restoring previous state when performing a decompression pass
with DCC enabled.

Note that we don't have to handle secondary command buffers
because we don't support this feature currently.

CC: 18.2 <mesa-stable@lists.freedesktop.org>
Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
(cherry picked from commit f3a78a9d)