sunxi: Pine64: temporarily remove extra Pine64 non-plus DT

sunxi: Pine64: temporarily remove extra Pine64 non-plus DT

With the merge of the new u-boot.itb size check now the build for
pine64_plus_defconfig breaks, as this file gets too large:
=============
u-boot.itb exceeds file size limit:
  limit:  516096 bytes
  actual: 521852 bytes
  excess: 5756 bytes
make: *** [u-boot.itb] Error 1
=============
One easily fixable reason is that we actually have two .dtbs in our FIT
image, one for the regular Pine64+ board, and one for the non-plus version.
The only difference U-Boot cares about is the 100Mbit Ethernet PHY used
on the non-plus version, however Ethernet isn't enabled in the non-plus
DT anyway.
So we could avoid the non-plus special handling, and remove that extra
.dtb from the FIT image, which saves a few KBs and brings us back below the
limit. The Pine64 would boot with a Pine64+ .dtb, and would fail to
enable Ethernet. Given that it didn't work in the first place, this is not
a regression.
Once we switch to a non-MMC environment, we can bring this back, then
with a proper .dtb and hopefully working Ethernet.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>