Fix: align CMAC output parameter and initialize key_index to remove compiler warnings

[dbarzin]

Summary:
This patch fixes two GCC warnings:

• cmac.c — align function parameter with header declaration
• mifare/mifarehost.c — initialize and guard key_index to silence “may be used uninitialized” and ensure safe access.

Result:

• No more -Warray-parameter in cmac.c
• No more uninitialized or unsafe access warning in mifarehost.c
• No API/ABI changes