armv7:TI: Add <asm/ti-common/sys_proto.h> and migrate omap_hw_init_context

armv7:TI: Add <asm/ti-common/sys_proto.h> and migrate omap_hw_init_context

The omap_hw_init_context function (and assorted helpers) is the same for
all OMAP-derived parts as when CHSETTINGS are used, that's the same and
our DDR base is also always the same.  In order to make this common we
simply need to update the names of the define for DDR address space
which is also common.

Cc: Sricharan R. <r.sricharan@ti.com>
Cc: Lokesh Vutla <lokeshvutla@ti.com>
Signed-off-by: Tom Rini <trini@ti.com>
Reviewed-by: Lokesh Vutla <lokeshvutla@ti.com>