nfp: Remove kernel.h when not needed

When kernel.h is used in the headers it adds a lot into dependency hell,
especially when there are circular dependencies are involved.

Remove kernel.h when it is not needed.
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Simon Horman <simon.horman@corigine.com>
Link: https://lore.kernel.org/r/20220607125103.487801-1-simon.horman@corigine.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/netronome/nfp/nfpcore/crc32.h

@@ -4,7 +4,6 @@
 #ifndef NFP_CRC32_H
 #define NFP_CRC32_H
 
-#include <linux/kernel.h>
 #include <linux/crc32.h>
 
 /**