ocfs2: eliminate a misreported warning

ocfs2: eliminate a misreported warning

The warning is invalid because the parameter chunksize passed from
ocfs2_info_freefrag_scan_chain-->ocfs2_info_update_ffg is guaranteed to
be positive.  So __ilog2_u32 cannot return -1.

  fs/ocfs2/ioctl.c: In function 'ocfs2_info_update_ffg':
  fs/ocfs2/ioctl.c:411:17: warning: array subscript is below array bounds [-Warray-bounds]
    hist->fc_chunks[index]++;
                   ^
  fs/ocfs2/ioctl.c:411:17: warning: array subscript is below array bounds [-Warray-bounds]

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Zhen Lei <[email protected]>
Reviewed-by: Andrew Morton <[email protected]>
Cc: Mark Fasheh <[email protected]>
Cc: Joel Becker <[email protected]>
Cc: Junxiao Bi <[email protected]>
Cc: Joseph Qi <[email protected]>
Cc: Changwei Ge <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>