ARM: vt8500: Add missing NULL terminator in dt_compat

When I tried booting a stih415 Dual core A9 with multi_v7_defconfig, it
failed to boot. The issues seems to be changing by enabling or disabling
VT8550 platform. Having a quick look at dt_compat list, it seems to miss
a NULL terminator, which means of_flat_dt_match will compat check will
cross the boundary of dt_compat and fault at some point , which is what
was happening in my case.

Without this patch if we try to boot multi_v7_defconfig you might notice
that some of the platforms might fault if they fall after vt8500 in
machine-desc list. Other platforms which fall before vt8500 in mdesc list
will not fault.
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@st.com>
Acked-by: Tony Prisk <linux@prisktech.co.nz>
Signed-off-by: Olof Johansson <olof@lixom.net>

arch/arm/mach-vt8500/vt8500.c

@@ -173,6 +173,7 @@ static const char * const vt8500_dt_compat[] = {
 	"wm,wm8505",
 	"wm,wm8750",
 	"wm,wm8850",
+	NULL
 };
 
 DT_MACHINE_START(WMT_DT, "VIA/Wondermedia SoC (Device Tree Support)")