tests: Increase testcases timeout for fvp_baser_aemv8r_smp

The tests/kernel/mem_protect/syscalls/ and tests/kernel/smp/ run too
slow on fvp_baser_aemv8r_smp. Increase the timeout_multiplier to 8 for
fvp_baser_aemv8r_smp.

Signed-off-by: Jaxson Han <jaxson.han@arm.com>