arm: K3: j721e: Fix boot parameter table index memory address

The boot parameter table index memory address for J721E was configured
to an incorrect value which prevented the use of this definition to
determine which boot parameter table is active which is needed to be
able to distinguish between primary and backup boot modes. Fix this
issue by updating the value to the correct one also in alignment with
the J721E Technical Reference Manual (TRM).

Signed-off-by: Andreas Dannenberg <dannenberg@ti.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>