feat(zynqmp): make stack size configurable

If PLATFORM_STACK_SIZE not already defined, use the default value of
PLATFORM_STACK_SIZE.
This makes the stack size value configurable for different interface
like custom packages.

Signed-off-by: Amit Nagal <amit.nagal@amd.com>
Signed-off-by: Akshay Belsare <akshay.belsare@amd.com>
Change-Id: I87e9fcbfb4c4092378b1ac0ff8fb6d084495d320
2 files changed