BeagleBoard: config: Switch to ttyO2

This is needed to support the latest kernel versions.

Cc: Albert ARIBAUD <albert.u.boot@aribaud.net>
Cc: Sandeep Paulraj <s-paulraj@ti.com>
Signed-off-by: Alexander Holler <holler@ahsoftware.de>
Signed-off-by: Dirk Behme <dirk.behme@gmail.com>
Signed-off-by: Tom Rini <trini@ti.com>
Signed-off-by: Sandeep Paulraj <s-paulraj@ti.com>