ARM: dts sunxi: Relax a bit the CMA pool allocation range

The hardware codec on the A10, A10s, A13 and A20 needs buffer in the
first 256MB of RAM. This was solved by setting the CMA pool at a fixed
address in that range.

However, in recent kernels there's something else that comes in and
reserve some range that end up conflicting with our default pool
requirement, and thus makes its reservation fail.

The video codec will then use buffers from the usual default pool,
outside of the range it can access, and will fail to decode anything.

Since we're only concerned about that 256MB, we can however relax the
allocation to just specify the range that's allowed, and not try to
enforce a specific address.

Fixes: 5949bc56 ("ARM: dts: sun4i-a10: Add Video Engine and reserved memory nodes")
Fixes: 96043201 ("ARM: dts: sun5i: Add Video Engine and reserved memory nodes")
Fixes: c2a641a7 ("ARM: dts: sun7i-a20: Add Video Engine and reserved memory nodes")
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Acked-by: Chen-Yu Tsai <wens@csie.org>
Link: https://lore.kernel.org/r/20200704130829.34297-1-maxime@cerno.tech