kmod-sched-cake: bump to latest bake of cake

There has been recent significant activity with the cake qdisc of late
but in the cobalt branch.  Some of that effort is related to upstreaming
to kernel & iproute2 mainline but we're not quite there yet.  Relevant
feature changes:

ingress mode: Instead of only counting packets that make it past the
shaper, include packets we've decided to drop as well, since they did
arrive with us on the link and took link capacity.
This mode is more suitable for shaping the ingress of a link
(e.g. from ISP) rather than the more normal egress.

ptm mode: Minor optimisation in packet overhead calculation.

dual-src/dsthost/triple-isolate: Optimise only calculating src or dst
host hashes only if required.

ack-filter/ack-filter-aggressive: Filter excessive TCP ACKS.  Useful in
highly assymetric links (downstream v upstream capacity) where the
majority of upstream link capacity is occupied with ACKS for downstream
traffic.

A separate iproute2 patch to teach it about Cake's new features will
follow.

Signed-off-by: Kevin Darbyshire-Bryant <ldir@darbyshire-bryant.me.uk>

package/kernel/kmod-sched-cake/Makefile

@@ -13,9 +13,9 @@ PKG_RELEASE:=1
 
 PKG_SOURCE_PROTO:=git
 PKG_SOURCE_URL:=https://github.com/dtaht/sch_cake.git
-PKG_SOURCE_DATE:=2017-11-20
-PKG_SOURCE_VERSION:=dfb2f6ccfbea7c413acec97d8440e344b94ca8e7
-PKG_MIRROR_HASH:=bbb62e5ff3b04b8e7734912a8768114f5a8cbc6c7763ca29cef7cbdbaa0e782f
+PKG_SOURCE_DATE:=2017-12-07
+PKG_SOURCE_VERSION:=49776da5b93f03c8548e26f2d7982d553d1d226c
+PKG_MIRROR_HASH:=d7bc6c333b43f6ff100a4b1d4593a18686fcdd6fd28a3aae55ea8bdad868b67f
 
 include $(INCLUDE_DIR)/package.mk