Remove const qualifier from AOM_QM seg matrices

This was causing visual stuido warnings when attempting to write
to seg_iqmatrix and seg_qmatrix using memcpy.

Change-Id: Idf12464c8c90c83af9c2b3ea399d739f7df3b5f9

av1/common/blockd.h

diff --git a/av1/common/blockd.h b/av1/common/blockd.h
index ebb20bb..e2fae11 100644
--- a/av1/common/blockd.h
+++ b/av1/common/blockd.h
@@ -632,8 +632,8 @@
   uint8_t width, height;
 
 #if CONFIG_AOM_QM
-  const qm_val_t *seg_iqmatrix[MAX_SEGMENTS][2][TX_SIZES_ALL];
-  const qm_val_t *seg_qmatrix[MAX_SEGMENTS][2][TX_SIZES_ALL];
+  qm_val_t *seg_iqmatrix[MAX_SEGMENTS][2][TX_SIZES_ALL];
+  qm_val_t *seg_qmatrix[MAX_SEGMENTS][2][TX_SIZES_ALL];
 #endif
   // encoder
   const int16_t *dequant;