davinci: Rearrange the da830/omap-l137 macros and functions

Rearrange the PINMUX macros and pinmux_setup function which
are common between da830/omap-l137 and da850/omap-l138.

Also, replace the da830 string in function names to da8xx.

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