davinci: soc-specific SRAM setup

Package on-chip SRAM.  It's always accessible from the ARM, so
set up a standardized virtual address mapping into a 128 KiB
area that's reserved for platform use.

In some cases (dm6467) the physical addresses used for EDMA are
not the same as the ones used by the ARM ... so record that info
separately in the SOC data, for chips (unlike the OMAP-L137)
where SRAM may be used with EDMA.

Other blocks of SRAM, such as the ETB buffer or DSP L1/L2 RAM,
may be unused/available on some system.  They are ignored here.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>