davinci: Add machine checks to DA8XX serial console init routines

This patch adds machine checks in the serial console init routines
for the DA8XX EVM boards.  This is needed because there are other
DA8XX based machines that use a different UART/tty as the console
and may be included in a common kernel build.

Signed-off-by: Michael Williamson <michael.williamson@criticallink.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>