ARM: ensure all sched_clock() implementations are notrace marked

ftrace requires sched_clock() to be notrace.  Ensure that all
implementations are so marked.  Also make sure that they include
linux/sched.h

Also ensure OMAP clocksource read functions are marked notrace as
they're used for sched_clock() too.

Tested-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Tested-by: Will Deacon <will.deacon@arm.com>
Tested-by: Mikael Pettersson <mikpe@it.uu.se>
Tested-by: Eric Miao <eric.y.miao@gmail.com>
Tested-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/mach-ixp4xx/common.c b/arch/arm/mach-ixp4xx/common.c
index 82fc003..e0b91d8 100644
--- a/arch/arm/mach-ixp4xx/common.c
+++ b/arch/arm/mach-ixp4xx/common.c
@@ -424,7 +424,7 @@
 /*
  * sched_clock()
  */
-unsigned long long sched_clock(void)
+unsigned long long notrace sched_clock(void)
 {
 	cycle_t cyc = ixp4xx_get_cycles(NULL);
 	struct clocksource *cs = &clocksource_ixp4xx;