softpipe: add missing sentinel to debug option array

Add DEBUG_NAMED_VALUE_END to finalize debug option array (see
lp_screen.c). Otherwise debug_get_flags_option might attempt to read
debug_named_value::name at an offset and SIGSEGV.

Signed-off-by: Heinrich Fink <hfink@snap.com>
Fixes: 991def0edc ("softpipe: Convert to comma-separated SOFTPIPE_DEBUG for debug options.")
Reviewed-by: Marcin Ślusarz <marcin.slusarz@intel.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11742>

src/gallium/drivers/softpipe/sp_screen.c

@@ -55,6 +55,7 @@ static const struct debug_named_value sp_debug_options[] = {
    {"no_rast",   SP_DBG_NO_RAST,    "no-ops rasterization, for profiling purposes"},
    {"use_llvm",  SP_DBG_USE_LLVM,   "Use LLVM if available for shaders"},
    {"use_tgsi",  SP_DBG_USE_TGSI,   "Request TGSI from the API instead of NIR"},
+   DEBUG_NAMED_VALUE_END
 };
 
 int sp_debug;