llc: Add missing include directive for struct timeval

While including time.h is sufficient with Ubuntu's current libc6
2.19, the correct (and portable) include file is sys/time.h.

This commit modifies the include directive in llc.h accordingly.

Fixes: Jenkins #600

Addresses:
    In file included from gprs_ms.h:28,
        from gprs_ms.cpp:22:
        llc.h:68: error: field 'recv_time' has incomplete type
        llc.h:69: error: field 'expire_time' has incomplete type

Sponsored-by: On-Waves ehf
1 file changed