ARM: OMAP2+: control: new APIs to configure boot address and mode

SCM contains boot addr and boot mode registers to control
other processors on different OMAP versions. It controls the
boot address and mode for DSP based subsystems like: IVA 2.1
(OMAP2430), IVA 2.2 (OMAP3) and DSP (OMAP4).

If contained within SCM registers, when a processor is
booting it uses BOOTADDR to start running the code at that
location. BOOTMOD register specifies a different set of
modes for the processor to execute when booting (from direct,
idle, self-loop, user and default).

Since there was no offset associated with OMAP4, this patch
defines it.

Signed-off-by: Omar Ramirez Luna <omar.luna@linaro.org>
Signed-off-by: Paul Walmsley <paul@pwsan.com>