stack: allow lock-free only on relevant architectures

stack: allow lock-free only on relevant architectures

Since commit 7911ba0473e0 ("stack: enable lock-free implementation for
aarch64"), lock-free stack is supported on arm64 but this description was
missing from the doxygen for the flag.

Currently it is impossible to detect programmatically whether lock-free
implementation of rte_stack is supported. One could check whether the
header guard for lock-free stubs is defined (_RTE_STACK_LF_STUBS_H_) but
that's an unstable implementation detail. Because of that currently all
lock-free ring creations silently succeed (as long as the stack header
is 16B long) which later leads to push and pop operations being NOPs.
The observable effect is that stack_lf_autotest fails on platforms not
supporting the lock-free. Instead it should just skip the lock-free test
altogether.

This commit adds a new errno value (ENOTSUP) that may be returned by
rte_stack_create() to indicate that a given combination of flags is not
supported on a current platform.
This is detected by checking a compile-time flag in the include logic in
rte_stack_lf.h which may be used by applications to check the lock-free
support at compile time.

Use the added RTE_STACK_LF_SUPPORTED flag to disable the lock-free stack
tests at the compile time.
Perf test doesn't fail because rte_ring_create() succeeds, however
marking this test as skipped gives a better indication of what actually
was tested.

Fixes: 7911ba0473e0 ("stack: enable lock-free implementation for aarch64")

Signed-off-by: Stanislaw Kardach <kda@semihalf.com>
Acked-by: Olivier Matz <olivier.matz@6wind.com>