sched/headers: Prepare to remove <linux/cred.h> inclusion from <linux/sched.h>

Add #include <linux/cred.h> dependencies to all .c files rely on sched.h
doing that for them.

Note that even if the count where we need to add extra headers seems high,
it's still a net win, because <linux/sched.h> is included in over
2,200 files ...

Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/net/dns_resolver/dns_query.c b/net/dns_resolver/dns_query.c
index ecc28cf..ab9fec00 100644
--- a/net/dns_resolver/dns_query.c
+++ b/net/dns_resolver/dns_query.c
@@ -37,8 +37,10 @@
 
 #include <linux/module.h>
 #include <linux/slab.h>
+#include <linux/cred.h>
 #include <linux/dns_resolver.h>
 #include <linux/err.h>
+
 #include <keys/dns_resolver-type.h>
 #include <keys/user-type.h>