configs: am62a: move stack and heap to HSM RAM

configs: am62a: move stack and heap to HSM RAM

Texas Instruments has begun enabling security setting on the SoCs they
produce to instruct ROM and TIFS to begin protecting the Security
Management Subsystem (SMS) from other binaries we load into the chip by
default.

One way ROM does this is by enabling firewalls to protect the OCSRAM
region it's using during bootup. Only after TIFS has started (and had
time to disable the OCSRAM firewall region) will we have write access to
the region.

This means we will need to move the stack & heap from OCSRAM to HSM RAM
and reduce the size of BSS and the SPL to allow it to fit properly.

Signed-off-by: Bryan Brattlof <bb@ti.com>