[non-normative] Fix warnings with !CONFIG_LOWPRECISION_BLEND

The compiler was complaining about the 'bd' parameter being
unused in two functions.

Change-Id: Iac2aa86234bb9554bb2dfa6ee6628bd1d09bfb1e

av1/common/convolve.h

diff --git a/av1/common/convolve.h b/av1/common/convolve.h
index ae66367..af0230a 100644
--- a/av1/common/convolve.h
+++ b/av1/common/convolve.h
@@ -111,6 +111,8 @@
   if (intbufrange > 16) {
     conv_params.round_0 += intbufrange - 16;
   }
+#else
+  (void)bd;
 #endif  // CONFIG_LOWPRECISION_BLEND
   return conv_params;
 }
@@ -136,6 +138,7 @@
     conv_params.round_1 -= intbufrange - 16;
   }
 #else
+  (void)bd;
   conv_params.round_1 = 0;
 #endif  // CONFIG_LOWPRECISION_BLEND
   // TODO(yunqing): The following dst should only be valid while