arm: k3: config.mk: Add missing dependencies on tispl.bin HS

When building for secure devices using non-buildman based image generation
the signed tispl.bin file is called tispl.bin_HS. Also build the unsigned
tispl.bin file as expected.

Signed-off-by: Andrew Davis <afd@ti.com>
Signed-off-by: Manorit Chawdhry <m-chawdhry@ti.com>