st/clover: Fix build after shrink of pipe_box

Fixes: 3dfe61e ("gallium: decrease the size of pipe_box - 24 -> 16 bytes")
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=100569
Signed-off-by: Aaron Watry <awatry@gmail.com>
Reviewed-by: Francisco Jerez <currojerez@riseup.net>
Tested-by: Vinson Lee <vlee@freedesktop.org>
1 file changed