ata: Replace inclusion of kernel.h by bits.h in the header

ata.h uses BIT() macro, hence bits.h must be included. Otherwise
there is no need to have kernel.h included, I do not see any
direct users of it in ata.h. Hence replace inclusion of kernel.h.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20210409153456.87798-1-andriy.shevchenko@linux.intel.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

include/linux/ata.h

@@ -13,7 +13,7 @@
 #ifndef __LINUX_ATA_H__
 #define __LINUX_ATA_H__
 
-#include <linux/kernel.h>
+#include <linux/bits.h>
 #include <linux/string.h>
 #include <linux/types.h>
 #include <asm/byteorder.h>