TI:am33xx: Create common config files for TI ARMv7 platforms, and AM33xx

We create two new files, include/configs/ti_armv7_common.h for all of
the common IP blocks and related features / commands we share in
virtually all of our platforms.  We then create
include/configs/ti_am335x_common.h for everything common to the am335x
SoC leaving just the board specific parts to
include/configs/ti_am335x_common.h.

Signed-off-by: Tom Rini <trini@ti.com>