sunxi: H616: dram: Improve address wrapping detection

sunxi: H616: dram: Improve address wrapping detection

It turns out that checking just one write is not enough. Due to
unexplained reasons scan procedure detected double the size. By making
16 dword writes and comparisons that never happens.

New procedure is also inverted. Instead of writing two different values
to base address and some offset and then reading both and comparing
values, simplify this by writing pattern at the base address and then
search for this pattern at some offset.

Signed-off-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Tested-by: Ryan Walklin <ryan@testtoast.com>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>