davinci: Move the da830/omap-l137 #defines to header file

With the introduction of TI da850/omap-l138, some of the macros
defined for da830/omap-l137 will be needed in da850 source file.
So, move the common macros to da8xx.h header file.

Also, modify the macro names from DA830_... to DA8XX_.

Signed-off-by: Sudhakar Rajashekhara <sudhakar.raj@ti.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>