ARMv7: enable L2 cache in proc_init

Since the L2 cache is disabled in proc_fin (see 56a92a31b3), it needs to be
enabled in proc_init when recovering from a kexec(). Without this, it will
remain disabled until cpuidle fixes it up during a transition, which could
be long after boot.

Signed-off-by: Richard Braakman <richard.braakman@jollamobile.com>