clocksource/integrator: Fix section mismatch warning

clocksource/integrator: Fix section mismatch warning

gcc-4.6 and older fail to inline integrator_clocksource_init, so they
end up showing a harmless warning:

WARNING: vmlinux.o(.text+0x4aa94c): Section mismatch in reference from the function integrator_clocksource_init() to the function .init.text:clocksource_mmio_init()
The function integrator_clocksource_init() references
the function __init clocksource_mmio_init().
This is often because integrator_clocksource_init lacks a __init
annotation or the annotation of clocksource_mmio_init is wrong.

Add the missing __init annotation that makes it build cleanly with all
compilers.

Signed-off-by: Arnd Bergmann <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Cc: Thierry Reding <[email protected]>
Cc: Linus Walleij <[email protected]>
Cc: Daniel Lezcano <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]