Add Cortex-A35 start by NS thread

Trusted Firmware-M v2.1.2

Trusted Firmware-M v2.1.1

Trusted Firmware-M v2.1.0

Build: Add stub functions of system calls

GNU Arm compiler version greater equal than *11.3.Rel1*
has a linker issue that required system calls are missing,
such as _read and _write. Add stub functions of required
system calls to solve this issue.

Signed-off-by: Chendi Sun <chendi.sun@arm.com>
Change-Id: I4280284b0a002d5e7765ef6a64cffa7542eb1274