plat: qemu: Update secure memory nodes instead of deleting

Trusty can parse the device tree now and read the location
of secure memory from it. Preserve the secure memory nodes
and replace their device type with secure-memory instead
of deleting them altogether.

Bug: 284057071
Change-Id: I501255398f7644bf4f8329933f9f4d6e3467ae17
1 file changed