LU-13802 llite: refactor ll_file_io_generic decs

LU-13802 llite: refactor ll_file_io_generic decs

The variable declarations in ll_file_io_generic are in no
order at all.  Put them in the standard order and convert
a few 'unsigned int' to bool.

Test-Parameters: trivial
Signed-off-by: Patrick Farrell <pfarrell@whamcloud.com>
Change-Id: I0b808ab82bdc129853dd4f27b93b3c91b201ca8a
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/52587
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Sebastien Buisson <sbuisson@ddn.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Shaun Tancheff <shaun.tancheff@hpe.com>