Implement 9p2000.L version of open(LOPEN) interface in qemu 9p server.

For LOPEN, no need to convert the flags to and from 9p mode to VFS mode.

Synopsis:

    size[4] Tlopen tag[2] fid[4] mode[4]

    size[4] Rlopen tag[2] qid[13] iounit[4]

Current qemu 9p server does not support following flags:
    O_NOCTTY, O_NONBLOCK, O_ASYNC & O_CLOEXEC

[Fix mode format - jvrao@linux.vnet.ibm.com]
Signed-off-by: NM. Mohan Kumar <mohan@in.ibm.com>
Signed-off-by: NVenkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>