lsm: constify 'bprm' parameter in security_bprm_committed_creds()

Three LSMs register the implementations for the 'bprm_committed_creds()'
hook: AppArmor, SELinux and tomoyo. Looking at the function
implementations we may observe that the 'bprm' parameter is not changing.

Mark the 'bprm' parameter of LSM hook security_bprm_committed_creds() as
'const' since it will not be changing in the LSM hook.

Signed-off-by: Khadija Kamran <kamrankhadijadj@gmail.com>
[PM: minor merge fuzzing due to other constification patches]
Signed-off-by: Paul Moore <paul@paul-moore.com>