davinci: Move interrupt ctlr info to SoC infrastructure

Use the SoC infrastructure to hold the interrupt controller
information (i.e., base address, default priorities,
interrupt controller type, and the number of IRQs).

The interrupt controller base, although initially put
in the soc_info structure's intc_base field, is eventually
put in the global 'davinci_intc_base' so the low-level
interrupt code can access it without a dereference.

These changes enable the SoC default irq priorities to be
put in the SoC-specific files, and the interrupt controller
to be at any base address.

Signed-off-by: Mark A. Greer <mgreer@mvista.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>