ARM: OMAP2+: SmartReflex: move the smartreflex header to include/linux/power

Move the smartreflex header file
(arch/arm/mach-omap2/smartreflex.h) in a new header file
include/linux/power/smartreflex.h.

This change makes the SmartReflex implementation ready for the move
to drivers/.

Signed-off-by: Jean Pihet <j-pihet@ti.com>
Signed-off-by: J Keerthy <j-keerthy@ti.com>
Reviewed-by: Kevin Hilman <khilman@ti.com>
Signed-off-by: Kevin Hilman <khilman@ti.com>