staging: lustre: Cleanup variable declarations in mdc_enqueue()

Changes:
- move const union vars to the top
- move rc to bottom
- do not initialize req
- set lvb_type to enum member instead of 0
- change __u64 to u64
- fix inconsistant columnization

Signed-off-by: Srikrishan Malik <srikrishanmalik@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>