bsc: split f_verify_encr_info() from f_cipher_mode()

The verification of correct encryption information so far is part of
f_cipher_mode(); put it in a separate new function f_verify_encr_info()
so that it can be re-used for handover channel activation.

Related: SYS#5324
Change-Id: I11602d23670f436a22b891fc744fe07e470f2b79
1 file changed