CC3XX: Tests: Fix errors when compiling with GCC14

GCC14 has upgraded some warnings to errors and therefore we need to fix
them in order to compile the tests.

These are the following:
- -Wimplicit-function-declaration. Note that in
  pka_test_virtual_registers we need to update the function call as the
  arguments passed are incorrect
- -Wreturn-mismatch

Change-Id: Icea54ceefd9265812e0bdbdb3b97af29d080ca20
Signed-off-by: Jackson Cooper-Driver <jackson.cooper-driver@arm.com>
5 files changed