arm, davinci: da850/dm365 lowlevel cleanup

- Cleanup a lot of fix values, and use defines instead.
- Also make some values configurable through the board config
  file.
- delete the NAND_SPL code for da850, as it is not used actually
- remove the asm code

Signed-off-by: Heiko Schocher <hs@denx.de>
Cc: Wolfgang Denk <hs@denx.de>
Cc: Sandeep Paulraj <s-paulraj@ti.com>
Cc: Albert ARIBAUD <albert.u.boot@aribaud.net>
Cc: Tom Rini <tom.rini@gmail.com>
Cc: Christian Riesch <christian.riesch@omicron.at>
Signed-off-by: Sandeep Paulraj <s-paulraj@ti.com>