unified: Fix semaphore group tests

Threads usings semaphore groups require a larger stack.

Also suppresses warnings in test_sema/microkernel due to Zephyr's
__printf_like() toolchain macro as variable types being printed
have changed between the microkernel and unified kernel.

Change-Id: If7490e0c68c299cc7a45010b9e6db7c01c826a6c
Signed-off-by: Peter Mitsis <peter.mitsis@windriver.com>