linux-phytec-ti

arm64: ti: Build all dtbos along with dtbs

It is pain to build each dtbo separately. So allow
dtbos to be build along with the commands 'dtbs'.
Also drop support for using dtb-merge.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Signed-off-by: Tero Kristo <t-kristo@ti.com>