xen: credit: rearrange members of control structures

xen: credit: rearrange members of control structures

With the aim of improving memory size and layout, and
at the same time trying to put related fields reside
in the same cacheline.

Here's a summary of the output of `pahole`, with and
without this patch, for the affected data structures.

csched_pcpu:
 * Before:
    size: 88, cachelines: 2, members: 6
    sum members: 80, holes: 1, sum holes: 4
    padding: 4
    paddings: 1, sum paddings: 5
    last cacheline: 24 bytes
 * After:
    size: 80, cachelines: 2, members: 6
    paddings: 1, sum paddings: 5
    last cacheline: 16 bytes

csched_vcpu:
 * Before:
    size: 72, cachelines: 2, members: 9
    padding: 2
    last cacheline: 8 bytes
 * After:
    same numbers, but move some fields to put
    related fields in same cache line.

csched_private:
 * Before:
    size: 152, cachelines: 3, members: 17
    sum members: 140, holes: 2, sum holes: 8
    padding: 4
    paddings: 1, sum paddings: 5
    last cacheline: 24 bytes
 * After:
    same numbers, but move some fields to put
    related fields in same cache line.

Signed-off-by: Dario Faggioli <dario.faggioli@citrix.com>
Acked-by: George Dunlap <george.dunlap@citrix.com>