arm: mach-k3: common: reorder removal of firewalls

K3 devices have some firewalls set up by ROM that we usually remove so
that the development is easy in HS devices.

While removing the firewalls disabling a background region before
disabling the foreground regions keeps the firewall in a state where all
the transactions will be blacklisted until all the regions are disabled.
This causes a race for some other entity trying to access that memory
region before all the firewalls are disabled and causes an exception.

Since there is no guarantee on where the background regions lie based on
ROM configurations or no guarantee if the background regions will allow
all transactions across the memory spaces, iterate the loop twice removing
the foregrounds first and then backgrounds.

Signed-off-by: Manorit Chawdhry <m-chawdhry@ti.com>