LU-6142 lov: cleanup unneeded macros from lov_request.c

LU-6142 lov: cleanup unneeded macros from lov_request.c

One macro defines a custom U64_MAX. The other adds
together two numbers, capping the sum at U64_MAX.
These macros are only used in a couple places. The
logic would be clearer and more concise without them.

Also, fix an incorrect comment.

Test-Parameters: trivial
Signed-off-by: Timothy Day <timday@amazon.com>
Change-Id: I31012fbddba459df909c27cde8c59461f013c3be
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/52014
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>