kmscube: bump version to fix build failures

Bump kmscube version to fix build failures such as this one seen on sparc64:
http://autobuild.buildroot.net/results/d7e/d7e82c67e0b04b0aea990bfb19dd6e4fd914bebe/build-end.log

,and also the one reported by Gary Bisson with Linaro 2017.02 ARM
gnueabihf toolchain.

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/kmscube/kmscube.hash

@@ -1,2 +1,2 @@
 # Locally computed
-sha256 aee8375da730c2e59e8644d6bd5e011f06c88f723a8f8934bd5dac67d94a3b8a  kmscube-87e3ff5683ee54228b3e6e75f7d4de83901fadb0.tar.gz
+sha256 dbd3eedd7fa518e3fc8bbcd424e408846a67c2c57661db30b3f5adb25f7e1513  kmscube-db8c6fc0f625e3a3d36731363276c459661d4149.tar.gz

package/kmscube/kmscube.mk

@@ -4,7 +4,7 @@
 #
 ################################################################################
 
-KMSCUBE_VERSION = 87e3ff5683ee54228b3e6e75f7d4de83901fadb0
+KMSCUBE_VERSION = db8c6fc0f625e3a3d36731363276c459661d4149
 KMSCUBE_SITE = https://cgit.freedesktop.org/mesa/kmscube/snapshot
 KMSCUBE_LICENSE = MIT
 KMSCUBE_DEPENDENCIES = host-pkgconf mesa3d libdrm