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: NSantosh Shilimkar <santosh.shilimkar@ti.com>
Tested-by: NWill Deacon <will.deacon@arm.com>
Tested-by: NMikael Pettersson <mikpe@it.uu.se>
Tested-by: NEric Miao <eric.y.miao@gmail.com>
Tested-by: NOlof Johansson <olof@lixom.net>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>