LU-18753 ldlm: remove unused stub functions

LU-18753 ldlm: remove unused stub functions

Remove:

ldlm_lock_fail_match()
ldlm_error2errno()
ldlm_pool_get_clv()
ldlm_pool_set_slv()
ldlm_imp2pl()

They are not called anywhere.

Fixes: e536e511c9e6 ("LU-5829 ldlm: remove unnecessary EXPORT_SYMBOL")
Fixes: fce887d1f9e0 ("b=15226")
Test-Parameters: trivial
Signed-off-by: Timothy Day <timday@amazon.com>
Change-Id: Iff93740206b1cf295d4500c8135ea1d2343f4b66
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/58264
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>