Disabling filter 0 causes inability to access DRAM.
An attempt leads to an abort.
ARM manual disallows to disable filter 0, but if we do
that from SRAM, nothing bad happens.
This patch prevents disabling of a filter 0, allowing to
reconfigure other filters from DRAM.
Note: this patch doesn't change the logic after reset.
It is only needed in case someone wants to reconfigure the
previously configured TZASC.
Change-Id: I196a0cb110a89afbde97f64a94df3101f28708a4
Signed-off-by: stsp@users.sourceforge.net
ef378d3ec1