buildroot

ti-cgt-pru: use HOST_TI_CGT_PRU_DL_DIR instead of TI_CGT_PRU_DL_DIR

The infrastructure only provides HOST_TI_CGT_PRU_DL_DIR, because this
package is host only. Ideally the infra should provide TI_CGT_PRU_DL_DIR,
but it doesn't currently, and that requires more significant changes.

Signed-off-by: Maxime Hadjinlian <maxime.hadjinlian@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>