LU-16518 ptlrpc: fix clang build errors

LU-16518 ptlrpc: fix clang build errors

Fixed bugs which cause errors on Clang.

The majority of changes involve adding
defines for the 'ptlrpc_nrs_ctl' enum.
This avoids having to explicitly cast
enums from one type to another.

An unused variable 'req' was removed from
'nrs_tbf_req_get'. A 'strlcpy' in
'sptlrpc_process_config' was copying the
wrong number of bytes. Another variable,
'rc' in 'sptlrpc_lproc_init', seemed to
be neglected unintentionally; this was also
fixed.

Lustre-change: https://review.whamcloud.com/49859
Lustre-commit: 50f28f81b5aa8f8ad1c8585bd7e262910f936e50

Signed-off-by: Timothy Day <timday@amazon.com>
Change-Id: If994c625199b392198f944f9cd21bbf2142bce69
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/54131
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>