package: don't use .xz format for github

Fixes http://autobuild.buildroot.net/results/955/955ed1af28f6ff9912adddc0342d1f3ca65e5b4d/

Commit 62146ea3ad (change package tarball compression to xz whenever possible)
changed a number of packages to use .xz format tarballs. Unfortunately this
doesn't work for packages from github, as it delivers gzip compressed tarballs
even when a .xz is requested.

Fix it by reverting this change for the packages using github.

Reported-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/cpuload/cpuload.mk

@@ -5,10 +5,8 @@
 ################################################################################
 
 CPULOAD_VERSION = v0.3
-CPULOAD_SOURCE = cpuload-$(CPULOAD_VERSION).tar.xz
 CPULOAD_SITE = http://github.com/kelvincheung/cpuload/tarball/$(CPULOAD_VERSION)
 CPULOAD_LICENSE = GPLv2
 CPULOAD_LICENSE_FILES = COPYING
 
-
 $(eval $(autotools-package))

package/fb-test-app/fb-test-app.mk

@@ -5,7 +5,6 @@
 ################################################################################
 
 FB_TEST_APP_VERSION = v1.0.0
-FB_TEST_APP_SOURCE = fb-test-app-$(FB_TEST_APP_VERSION).tar.xz
 FB_TEST_APP_SITE = http://github.com/prpplague/fb-test-app/tarball/$(FB_TEST_APP_VERSION)
 FB_TEST_APP_LICENSE = GPLv2
 FB_TEST_APP_LICENSE_FILES = COPYING

package/input-event-daemon/input-event-daemon.mk

@@ -5,7 +5,6 @@
 ################################################################################
 
 INPUT_EVENT_DAEMON_VERSION = v0.1.3
-INPUT_EVENT_DAEMON_SOURCE = input-event-daemon-$(INPUT_EVENT_DAEMON_VERSION).tar.xz
 INPUT_EVENT_DAEMON_SITE = http://github.com/gandro/input-event-daemon/tarball/$(INPUT_EVENT_DAEMON_VERSION)
 INPUT_EVENT_DAEMON_LICENSE = input-event-daemon license
 INPUT_EVENT_DAEMON_LICENSE_FILES = README