Renames interface field in VpxInterface

Renames interface to codec_interface since it is a reserved
word on windows.

Change-Id: I84f2cbf257a4c44f16dc2464127e35ee405c2c3e
diff --git a/tools_common.h b/tools_common.h
index 6a9f4f7..558413e 100644
--- a/tools_common.h
+++ b/tools_common.h
@@ -120,7 +120,7 @@
 typedef struct VpxInterface {
   const char *const name;
   const uint32_t fourcc;
-  vpx_codec_iface_t *(*const interface)();
+  vpx_codec_iface_t *(*const codec_interface)();
 } VpxInterface;
 
 int get_vpx_encoder_count();