Fix counter of fixed keyframe distance

When the keyframe distance is fixed the first interval has the right
distance but, the next ones have kf_distance + 1.

Change-Id: I44f1190fe7146124bd07660a5e0ef08829e3ae07

vp8/vp8_cx_iface.c

diff --git a/vp8/vp8_cx_iface.c b/vp8/vp8_cx_iface.c
index b23bd95..29c6444 100644
--- a/vp8/vp8_cx_iface.c
+++ b/vp8/vp8_cx_iface.c
@@ -706,7 +706,7 @@
         if (++ctx->fixed_kf_cntr > ctx->cfg.kf_min_dist)
         {
             flags |= VPX_EFLAG_FORCE_KF;
-            ctx->fixed_kf_cntr = 0;
+            ctx->fixed_kf_cntr = 1;
         }
     }