LU-8191 libcfs: convert functions to static, removed function

LU-8191 libcfs: convert functions to static, removed function

Static analysis shows that a number of functions
could be made static. This patch declares several
functions in libcfs static.

Remove cfs_expr_list_values_free in string.c, since
it is not used.

A header was missing in param.c, causing a number of
functions to be missing declarations.

Test-Parameters: trivial
Signed-off-by: Timothy Day <timday@amazon.com>
Change-Id: Ia580881efa806bde49d532e5b2d8f5097f2294e0
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/51428
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-by: Patrick Farrell <pfarrell@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>