package: don't use BR2_KERNEL_MIRROR for git downloads

The git repositories are not served on the kernel.org CDN:

    fatal: repository 'https://cdn.kernel.org/pub/scm/linux/kernel/git/will/kvmtool.git/' not found

Switch to explicitly use the git.kernel.org server.

Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
Cc: Matt Weber <matthew.weber@rockwellcollins.com>
Cc: Cyril Bur <cyrilbur@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/kvm-unit-tests/kvm-unit-tests.mk

@@ -5,7 +5,7 @@
 ################################################################################
 
 KVM_UNIT_TESTS_VERSION = kvm-unit-tests-20171020
-KVM_UNIT_TESTS_SITE = $(BR2_KERNEL_MIRROR)/scm/virt/kvm/kvm-unit-tests.git
+KVM_UNIT_TESTS_SITE = https://git.kernel.org/pub/scm/virt/kvm/kvm-unit-tests.git
 KVM_UNIT_TESTS_SITE_METHOD = git
 KVM_UNIT_TESTS_LICENSE = LGPL-2.0
 KVM_UNIT_TESTS_LICENSE_FILES = COPYRIGHT

package/kvmtool/kvmtool.mk

@@ -5,7 +5,7 @@
 ################################################################################
 
 KVMTOOL_VERSION = f77d646ba01d04be5aad9449ac00719c043fe36e
-KVMTOOL_SITE = $(BR2_KERNEL_MIRROR)/scm/linux/kernel/git/will/kvmtool.git
+KVMTOOL_SITE = https://git.kernel.org/pub/scm/linux/kernel/git/will/kvmtool.git
 KVMTOOL_SITE_METHOD = git
 KVMTOOL_DEPENDENCIES = \
 	$(if $(BR2_PACKAGE_BINUTILS),binutils) \