config: add option to enable asserts

config: add option to enable asserts

Currently, enabling assertion have to set CONFIG_RTE_LOG_LEVEL to
RTE_LOG_DEBUG. CONFIG_RTE_LOG_LEVEL is the default log level of control
path, RTE_LOG_DP_LEVEL is the log level of data path. It's a little bit
hard to understand literally that assertion is decided by control path
LOG_LEVEL, especially assertion used on data path.

On the other hand, DPDK need an assertion enabling switch w/o impacting
log output level, assuming "--log-level" not specified.

Assertion is an important API to balance DPDK high performance and
robustness. To promote assertion usage, it's valuable to unhide
assertion out of COFNIG_RTE_LOG_LEVEL.

In one word, log is log, assertion is assertion, debug is hot pot :)

Rationale of this patch is to introduce an dedicate switch of
assertion: RTE_ENABLE_ASSERT

Signed-off-by: Xueming Li <xuemingl@mellanox.com>
Acked-by: Gaetan Rivet <gaetan.rivet@6wind.com>