arm64: switch to Kernel 4.1

arm64: switch to Kernel 4.1

- fix Kernel dts subdir location
- enable virtio networking
  we are using -M virt which supports virtio devices

changes in symbols due to make kernel_oldconfig:

- CONFIG_ARCH_BINFMT_ELF_RANDOMIZE_PIE=y : removed
fix security: upstream id: d1fd836dcf00d2028c700c7e44d2c23404062c90

- CONFIG_ARM64_CPU_SUSPEND: removed
commit id: af3cfdbf56b91785650f54e7c9a899d814b4b9fb

- CONFIG_ARM64_PGTABLE_LEVELS=3 : renamed PGTABLE_LEVELS
commit id: 9f25e6ad58e1fb3b4d441e4c55635c4598a6fa94

- CONFIG_GENERIC_CLOCKEVENTS_BUILD=y : removed upstream
commit id: 9f083b74df3a7eaa100b456f2dc195512daf728e

-# CONFIG_PREEMPT_RCU: unnecessary

unknown remove reasons:
-CONFIG_GENERIC_IOMAP=y
-# CONFIG_POWER_RESET_GPIO is not set
-# CONFIG_POWER_RESET_GPIO_RESTART is not set
-# CONFIG_POWER_RESET_LTC2952 is not set
-# CONFIG_POWER_RESET_SYSCON is not set
-# CONFIG_XEN is not set

tested and boot, networking work with qemu

Signed-off-by: Dirk Neukirchen <dirkneukirchen@web.de>
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@47005 3c298f89-4303-0410-b956-a3cf2f4a3e73