bus: omap_l3_noc: introduce concept of submodule

While OMAP4 and OMAP5 had 3 separate clock domains, DRA7 has only 2
and the first one then is internally divided into 2 sub clock domains.

To better represent this in the driver, we use the concept of submodule.

The address defintions in the devicetree is as per the high level
clock domain(module) base, the sub clockdomain/subdomain which shares
the same register space of a clockdomain is marked in the SoC data as
L3_BASE_IS_SUBMODULE.

L3_BASE_IS_SUBMODULE is used as an indication that it's base address is
the same as the parent module and offsets are considered from the same
base address as they are usually intermingled.

Other than the base address, the submodule is same as a module as it is
functionally so.

Signed-off-by: Nishanth Menon <nm@ti.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Tested-by: Darren Etheridge <detheridge@ti.com>
Tested-by: Sekhar Nori <nsekhar@ti.com>