doc: board: ti: k3: Fix up OpenOCD references and debug info

Fix minor path and config macro name updates to sync with latest
OpenOCD and U-Boot configurations.

Fixes: effe5085 ("doc: board: ti: k3: Add a guide to debugging with OpenOCD")
Signed-off-by: Jonathan Humphreys <j-humphreys@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>