meson: use dep_thread instead of dependency('threads') in freedreno

They are the same thing, but this is more consistent with the rest of
the project.

Signed-off-by: Dylan Baker <dylanx.c.baker@intel.com>
Reviewed-by: Eric Engestrom <eric.engestrom@imgtec.com>

src/gallium/drivers/freedreno/meson.build

@@ -217,7 +217,7 @@ ir3_compiler = executable(
   dependencies : [
     dep_libdrm,
     dep_libdrm_freedreno,
-    dependency('threads'),
+    dep_thread,
     dep_lmsensors,
   ],
   link_with : [