panfrost/drm: Check allocation size is positive

Zero-sized allocations will fail with an unhelpful errno from the
kernel; check size explicitly in userspace before it gets that far.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>

src/gallium/drivers/panfrost/pan_drm.c

@@ -84,6 +84,10 @@ panfrost_drm_create_bo(struct panfrost_screen *screen, size_t size,
                        uint32_t flags)
 {
         struct panfrost_bo *bo = rzalloc(screen, struct panfrost_bo);
+
+        /* Kernel will fail (confusingly) with EPERM otherwise */
+        assert(size > 0);
+
         struct drm_panfrost_create_bo create_bo = {
                 .size = size,
                 .flags = flags,