printk: Remove ratelimit.h from kernel.h

printk: Remove ratelimit.h from kernel.h

Decouple kernel.h from ratelimit.h: the global declaration of
printk's ratelimit_state is not needed, and it leads to messy
circular dependencies due to ratelimit.h's (new) adding of a
spinlock_types.h include.

Cc: Peter Zijlstra <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: David S. Miller <[email protected]>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <[email protected]>