vp9 asserts: fix compile warning

string literal to int within an assert

Change-Id: I0c889256b67a078e6e2a79577f0b7ae084243258
diff --git a/vp9/decoder/vp9_decodeframe.c b/vp9/decoder/vp9_decodeframe.c
index 56b05ce..b14f1ef 100644
--- a/vp9/decoder/vp9_decodeframe.c
+++ b/vp9/decoder/vp9_decodeframe.c
@@ -266,7 +266,7 @@
         vp9_idct32x32_add(dqcoeff, dst, stride, eob);
         break;
       default:
-        assert(!"Invalid transform size");
+        assert(0 && "Invalid transform size");
     }
 
     if (eob == 1) {
@@ -507,7 +507,7 @@
         decode_modes_sb(cm, xd, tile, mi_row + hbs, mi_col + hbs, r, subsize);
         break;
       default:
-        assert(!"Invalid partition type");
+        assert(0 && "Invalid partition type");
     }
   }