doc: ti: reorganize existing ti docs

Texas Instruments produces quite a lot of SoCs based upon a common
architecture 'generation'. (eg: OMAP, K3) TI's existing documentation
layout makes noticing this generation jump rather difficult.

To make navigation easier, split the existing documentation into
individual SoC families so we may begin grouping them according to their
generational (eg: OMAP, K3) families.

Signed-off-by: Bryan Brattlof <bb@ti.com>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>