lmkd: Add library function to unregister a process

Introduce lmkd_unregister_proc helper function. Fix a bug where
lmkd_pack_set_procremove used a wrong structure as a parameter.

Bug: 129011369
Test: verify process record removal when it is manually killed
Change-Id: I7ab5a499f6b1c6eecfdba4d0a5ec916053e2726a
Signed-off-by: Suren Baghdasaryan <surenb@google.com>