coresight: Fix implicit inclusion of linux/sched.h

The patch "Coresight: Add an interface for supporting ETM3/4 Context ID
tracing" adds uses of find_task_by_vpid() and task_pid_nr() from
linux/sched.h but does not include that header causing build errors in
at least an ARM allmodconfig where it is not implicitly included. Add an
explicit include to fix that.
Signed-off-by: NMark Brown <broonie@kernel.org>
Signed-off-by: NMathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

include/linux/coresight.h

@@ -14,6 +14,7 @@
 #define _LINUX_CORESIGHT_H
 
 #include <linux/device.h>
+#include <linux/sched.h>
 
 /* Peripheral id registers (0xFD0-0xFEC) */
 #define CORESIGHT_PERIPHIDR4	0xfd0