kernel.h is included solely for some other existing headers.
Include them directly and get rid of kernel.h.

While at it, sort headers alphabetically for easier maintenance.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Kurt Kanzenbach <kurt@linutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>