event/opdl: fix build using C99 mode
event/opdl: fix build using C99 mode

RHEL 7.4 gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-16)

‘for’ loop initial declarations are only allowed in C99 mode

Fixes: 4236ce9bf5bf ("event/opdl: add OPDL ring infrastructure library")

Signed-off-by: Andrew Rybchenko <ac94ab2a8fe9a9a087f6e24dcbc16626b52c07e8@solarflare.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk