arm64: Add NOLOAD attribute NOLOAD to .bss sections

Mark explicitly bss sections to not be loaded at
run time.
The similar patch was done in past by:
"Fix linker scripts: add NOLOAD atribute to .bss/.sbss sections"
(sha1: 64134f01)

The problem is related to latest toolchain added to Xilinx
v2017.1 design tools where jtag loader is trying to access
ununitialized memory.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>