ARM64: dts: meson-gx: Add firmware reserved memory zones

The Amlogic Meson GXBB/GXL/GXM secure monitor uses part of the memory space,
this patch adds these reserved zones.

Without such reserved memory zones, running the following stress command :
$ stress-ng --vm 16 --vm-bytes 128M --timeout 10s
multiple times:

Could lead to the following kernel crashes :
[   46.937975] Bad mode in Error handler detected on CPU1, code 0xbf000000 -- SError
...
[   47.058536] Internal error: Attempting to execute userspace memory: 8600000f [#3] PREEMPT SMP
...
Instead of the OOM killer.

Fixes: 4f24eda8 ("ARM64: dts: Prepare configs for Amlogic Meson GXBaby")
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Andreas Färber <afaerber@suse.de>
[khilman: added Fixes tag, added _reserved and unit addresses]
Signed-off-by: Kevin Hilman <khilman@baylibre.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>