locking/lockdep: Delete unnecessary #include

Commit:

  c3bc8fd6 ("tracing: Centralize preemptirq tracepoints and unify their usage")

added the inclusion of <trace/events/preemptirq.h>.

liblockdep doesn't have a stub version of that header so now fails to build.

However, commit:

  bff1b208 ("tracing: Partial revert of "tracing: Centralize preemptirq tracepoints and unify their usage"")

removed the use of functions declared in that header. So delete the #include.
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sasha Levin <alexander.levin@verizon.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Fixes: bff1b208 ("tracing: Partial revert of "tracing: Centralize ...")
Fixes: c3bc8fd6 ("tracing: Centralize preemptirq tracepoints ...")
Link: http://lkml.kernel.org/r/20180828203315.GD18030@decadent.org.ukSigned-off-by: Ingo Molnar <mingo@kernel.org>

kernel/locking/lockdep.c

@@ -55,7 +55,6 @@
 
 #include "lockdep_internals.h"
 
-#include <trace/events/preemptirq.h>
 #define CREATE_TRACE_POINTS
 #include <trace/events/lock.h>