mk: rename test related rules

mk: rename test related rules

Make rules renamed to a common syntax, test-x:
fast_test    -> test-fast
ring_test    -> test-ring
mempool_test -> test-mempool
perf_test    -> test-perf

These are to run various sub-set of the unit tests.

Not touched to make rules that are already following the syntax:
test-basic
test-build
test

Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>