feat(plat/zynqmp): disable the -mbranch-protection flag

With new gcc11.2 by default the -mbranch-protection is
set to "standard" which is leading to increase the text
section by 4Kb. As the ZynqMP uses the ARMv8 architecture,
so there is no impact when we disable the branch protection.
These instructions do not provide the branch protection in
architectures before Armv8.3-A.

Signed-off-by: Venkatesh Yadav Abbarapu <venkatesh.abbarapu@xilinx.com>
Acked-by: Michal Simek <michal.simek@xilinx.com>
Change-Id: I36f7a55abf99f50df2ee265255598d83b1f480c6