plat: xilinx: versal: Remove cortex-a53 compilation

Versal is a72 based that's why there is no reason to build low level
assemble code for a53.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Change-Id: Iff9cf2582102d951825b87fd9af18e831ca717d6
1 file changed