Replace cpi->common with preset variable cm

This commit replaces a few use cases of cpi->common with preset
variable cm, to avoid unnecessary pointer fetch in the non-RD
coding mode.

Change-Id: I4038f1c1a47373b8fd7bc5d69af61346103702f6

vp9/encoder/vp9_pickmode.c

diff --git a/vp9/encoder/vp9_pickmode.c b/vp9/encoder/vp9_pickmode.c
index f3b2d2f..887e461 100644
--- a/vp9/encoder/vp9_pickmode.c
+++ b/vp9/encoder/vp9_pickmode.c
@@ -241,9 +241,9 @@
   mbmi->ref_frame[0] = NONE;
   mbmi->ref_frame[1] = NONE;
   mbmi->tx_size = MIN(max_txsize_lookup[bsize],
-                      tx_mode_to_biggest_tx_size[cpi->common.tx_mode]);
-  mbmi->interp_filter = cpi->common.interp_filter == SWITCHABLE ?
-                        EIGHTTAP : cpi->common.interp_filter;
+                      tx_mode_to_biggest_tx_size[cm->tx_mode]);
+  mbmi->interp_filter = cm->interp_filter == SWITCHABLE ?
+                        EIGHTTAP : cm->interp_filter;
   mbmi->skip = 0;
   mbmi->segment_id = segment_id;