arm64: zynqmp: Rename zc1275/zcu1275 to be aligned with DT name

Folder names corresponds to DT name. These boards have been renamed from
zc1275 to zcu1275 by commit shown below and this should be the part of that
commit.

Fixes: 420d4467 ("arm64: zynqmp: Rename zc1275 to zcu1275")
Signed-off-by: Michal Simek <michal.simek@xilinx.com>