davinci: da8xx: Add base DA830/OMAP-L137 SoC support

davinci: da8xx: Add base DA830/OMAP-L137 SoC support

The da830/omap l137 is a new SoC from TI that is similar
to the davinci line.  Since its so similar to davinci,
put the support for the da830 in the same directory as
the davinci code.

There are differences, however.  Some of those differences
prevent support for davinci and da830 platforms to work
in the same kernel binary.  Those differences are:

1) Different physical address for RAM.  This is relevant
   to Makefile.boot addresses and PHYS_OFFSET.  The
   Makefile.boot issue isn't truly a kernel issue but
   it means u-boot won't work with a uImage including
   both architectures.  The PHYS_OFFSET issue is
   addressed by the "Allow for runtime-determined
   PHYS_OFFSET" patch by Lennert Buytenhek but it
   hasn't been accepted yet.

2) Different uart addresses.  This is only an issue
   for the 'addruart' assembly macro when CONFIG_DEBUG_LL
   is enabled.  Since the code in that macro is called
   so early (e.g., by _error_p in kernel/head.S when
   the processor lookup fails), we can't determine what
   platform the kernel is running on at runtime to use
   the correct uart address.

These areas have compile errors intentionally inserted
to indicate to the builder they're doing something wrong.

A new config variable, CONFIG_ARCH_DAVINCI_DMx, is added
to distinguish between a true davinci architecture and
the da830 architecture.

Note that the da830 currently has an issue with writeback
data cache so CONFIG_CPU_DCACHE_WRITETHROUGH should be
enabled when building a da830 kernel.

Additional generalizations for future SoCs in the da8xx family done by
Sudhakar Rajashekhara and Sekhar Nori.

Signed-off-by: Steve Chen <schen@mvista.com>
Signed-off-by: Mikhail Cherkashin <mcherkashin@ru.mvista.com>
Signed-off-by: Mark A. Greer <mgreer@mvista.com>
Cc: Sudhakar Rajashekhara <sudhakar.raj@ti.com>
Cc: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>