ethdev: fix build when vtune profiling is on

ethdev: fix build when vtune profiling is on

Add the previous prototype for the 'profile_hook_rx_burst_cb' function
to fix the compiler warning when the DPDK is built with
'RTE_ETHDEV_PROFILE_WITH_VTUNE' config option enabled:
/home/dpdk/lib/librte_ethdev/ethdev_profile.c:17:1: warning:
no previous prototype for profile_hook_rx_burst_cb [-Wmissing-prototypes]

Fixes: 2c1bbab7f09d ("ethdev: change vtune profiling approach")
Cc: stable@dpdk.org
Signed-off-by: Eugeny Parshutin <eugeny.parshutin@linux.intel.com>
Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>