[CORE] block: Add vmm_blockdev_flush_cache() API

Signed-off-by: Anup Patel <anup@brainfault.org>
[LIBS] vfs: Flush block device upon msync() on ext2fs and fatfs

Signed-off-by: Anup Patel <anup@brainfault.org>
[EMULATORS] virtio: Increase VIRTIO_DEVICE_MAX_NAME_LEN

Signed-off-by: Anup Patel <anup@brainfault.org>
[EMULATORS] Cleanup virtio_net.h and virtio_console.h

Signed-off-by: Anup Patel <anup@brainfault.org>
[CORE] devtree: Add blkdev string attribute for specifying block device name or path

Signed-off-by: Anup Patel <anup@brainfault.org>
[EMULATORS] virtio_queue: Simplify virtio_queue_get_iovec() and introduce virtio_queue_get_head_iovec()

The upcoming virtio block emulator requires virtio_queue_get_head_iovec() API.

Also, virtio_queue_get_head_iovec() is more generic hence virtio_queue_get_iovec() is implemented using virtio_queue_get_head_iovec()

Signed-off-by: Anup Patel <anup@brainfault.org>
Merge remote-tracking branch 'upstream/master' into dev_exynos4