arm: mach-k3: j721e: Fix unlocking control module registers

In main control mmr there is no partition 4 and partition 6 is available
only on J721e. Fix the same in ctrl_mmr_unlock function

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Reviewed-by: Suman Anna <s-anna@ti.com>