LU-13134 obdclass: re-declare cl_page variables to reduce its size

With following changes:
1) make CPS_CACHED declare start from 1 consistent with CPT_CACHED
2) add CPT_NR to indicate max allowed CPT state value.
3) Reserve 4 bits for @cp_state which allow 15 kind of states
4) Reserve 2 bits for @cp_type which allow 3 kinds of cl_page types
5) use short int for @cp_kmem_index and We still have another 16 bits
reserved for future extension.
6)move @cp_lov_index after @cp_ref to fill 4 bytes hole.

After this patch, cl_page size could reduce from 336 bytes to 320 bytes

Change-Id: I92d5652a42850890ac6ce61e54884450dda25cc7
Signed-off-by: Wang Shilong <wshilong@ddn.com>
Reviewed-on: https://review.whamcloud.com/37480
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>