vlib: fail in runtime if workers > nelts

vlib: fail in runtime if workers > nelts

Type: fix

With a release build, if you configure more than 55 workers, vpp
will start, but will corrupt memory as a lot of internal datastrctures
are allocated with assumption that there will be not more than
FRAME_QUEUE_MAX_NELTS threads.

Add a warning if amount of configured workers more than MAX_NELTS.

Anticipate that next commit would add a compile-time configurable
variable and name it VPP_MAX_THREADS.

Change-Id: I015f4f9aa5e8b828c7d90c90142d7a7c1ce68f97
Signed-off-by: Vladimir Smirnov <[email protected]>