Remove ATTRIBUTE_PACKED from InterpFilter which broke something

The ATTRIBUTE_PACKED caused something to break in MB_MODE_INFO.
boundary_info got corrupted and moving InterpFilter around in
MB_MODE_INFO could cause a segfault or the problems to go away (for
instance by moving InterpFilter to the end of the struct).  Perhaps
something in MB_MODE_INFO is sensitive to alignment.  This should be
investigated further and get fixed or documented, but for now remove
the attribute.

Change-Id: Ic4326ab98fe784d9b7d2b47d8f086b8429cedee9

av1/common/filter.h

diff --git a/av1/common/filter.h b/av1/common/filter.h
index fa2a348..50139d8 100644
--- a/av1/common/filter.h
+++ b/av1/common/filter.h
@@ -23,7 +23,7 @@
 
 #define USE_TEMPORALFILTER_12TAP 1
 
-typedef enum ATTRIBUTE_PACKED {
+typedef enum {
   EIGHTTAP_REGULAR,
   EIGHTTAP_SMOOTH,
   MULTITAP_SHARP,