docs: qemu: remove unneeded root=/dev/vda2 kernel parameter

In my understanding, /dev/vda2 does not exist unless you add
virtio drive to the qemu command line.

The rootfs is already specified by '-initrd rootfs.cpio.gz'.

Change-Id: Ifdca5d4f3819d87ef7e8a08ed870872d24b86370
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
1 file changed