kunit: replace kernel.h with the necessary inclusions

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

Replace kernel.h inclusion with the list of what is really being used.

Link: https://lkml.kernel.org/r/20211213204441.56204-1-andriy.shevchenko@linux.intel.comSigned-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Brendan Higgins <brendanhiggins@google.com>
Tested-by: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/kunit/assert.h

@@ -10,7 +10,7 @@
 #define _KUNIT_ASSERT_H
 
 #include <linux/err.h>
-#include <linux/kernel.h>
+#include <linux/printk.h>
 
 struct kunit;
 struct string_stream;