Include vpx_config.h in vpx_timer.h

vpx_timer.h uses several defines from the config file including
CONFIG_OS_SUPPORT and INLINE

Change-Id: I16cb45237787cbc1ae79a67e16b8042811dda336

vpx_ports/vpx_timer.h

@@ -11,6 +11,9 @@
 
 #ifndef VPX_PORTS_VPX_TIMER_H_
 #define VPX_PORTS_VPX_TIMER_H_
+
+#include "./vpx_config.h"
+
 #include "vpx/vpx_integer.h"
 
 #if CONFIG_OS_SUPPORT