log: fix log level regexp matching

log: fix log level regexp matching

Fix misuse of regular expression functions, which was producing a
segfault.

After the patch, it works properly:

  $ ./build/app/test --no-huge --log-level=pmd,3
  RTE>>dump_log_types
  [...]
  id 30: user7, level is debug
  id 31: user8, level is debug
  id 32: pmd.i40e.init, level is critical
  id 33: pmd.i40e.driver, level is critical

Coverity issue: 143472
Fixes: a5279180f510 ("eal: change several log levels matching a regexp")

Reported-by: Jianfeng Tan <jianfeng.tan@intel.com>
Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
Acked-by: Ferruh Yigit <ferruh.yigit@intel.com>