ti: k3: common: Remove use of ARM platform code

A recent patch[0] has made setting up page tables into generic
code, complete the conversion for TI platforms by removing the
use of plat_arm_get_mmap() and using the mmap table directly.

[0] 0916c38d ("Convert arm_setup_page_tables into a generic helper")

Signed-off-by: Andrew F. Davis <afd@ti.com>