soc: ti: pruss: fix referenced node in error message

So far, "(null)" is reported for the node that is missing clocks.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Acked-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Link: https://lore.kernel.org/r/d6e24953-ea89-fd1c-6e16-7a0142118054@siemens.com