panvk: add PANVK_DEBUG=force_blackhole

This flag is intended to be used by sparse resource creation. When
set, sparse resources will always start off mapped to blackhole,
regardless of whether they were created with SPARSE_RESIDENCY flag
set or not.

Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/35287>

src/panfrost/vulkan/panvk_instance.c

@@ -42,6 +42,7 @@ static const struct debug_control panvk_debug_options[] = {
    {"copy_gfx", PANVK_DEBUG_COPY_GFX},
    {"force_simultaneous", PANVK_DEBUG_FORCE_SIMULTANEOUS},
    {"implicit_others_inv", PANVK_DEBUG_IMPLICIT_OTHERS_INV},
+   {"force_blackhole", PANVK_DEBUG_FORCE_BLACKHOLE},
    {NULL, 0}};
 
 VKAPI_ATTR VkResult VKAPI_CALL

src/panfrost/vulkan/panvk_instance.h

@@ -26,6 +26,7 @@ enum panvk_debug_flags {
    PANVK_DEBUG_COPY_GFX = 1 << 9,
    PANVK_DEBUG_FORCE_SIMULTANEOUS = 1 << 10,
    PANVK_DEBUG_IMPLICIT_OTHERS_INV = 1 << 11,
+   PANVK_DEBUG_FORCE_BLACKHOLE = 1 << 12,
 };
 
 #if defined(VK_USE_PLATFORM_WAYLAND_KHR) || \