Update pl310 node in Armada 38x DTS to match the one used in Linux

Since the cache controller nodes fixup is added to the platform code,
this patch aligns it to the Linux device tree representation.

Submitted by: Patryk Duda <pdk@semihalf.com>
Reviewed by: cognet (mentor)
Approved by: cognet (mentor)
Obtained from: Semihalf
Differential Revision: https://reviews.freebsd.org/D11884