compiler.h: replace QEMU_SENTINEL with G_GNUC_NULL_TERMINATED

One less qemu-specific macro. It also helps to make some headers/units
only depend on glib, and thus moved in standalone projects eventually.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 797738a..ddc6003 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -225,7 +225,7 @@
 			volatile|
 			QEMU_NORETURN|
 			G_GNUC_WARN_UNUSED_RESULT|
-			QEMU_SENTINEL|
+			G_GNUC_NULL_TERMINATED|
 			QEMU_PACKED|
 			G_GNUC_PRINTF
 		  }x;