fix(zynqmp): move debug bl31 based address back to OCM

The commit 389594df ("fix(zynqmp): move bl31 with DEBUG=1 back to OCM")
tried to move address to OCM but address was actually out of OCM and likely
it was typo. Correct default address should be 0xfffe5000. If TF-A size is
bigger please select location DDR which should be fine for DEBUG cases.

Reported-by: Vesa Jääskeläinen <vesa.jaaskelainen@vaisala.com>
Signed-off-by: Michal Simek <michal.simek@amd.com>
Change-Id: I055f3a59cdca527f6029fcc2a19d76be35924d24