LU-7515 obdclass: add export for lprocfs_stats_alloc_one()

LU-7515 obdclass: add export for lprocfs_stats_alloc_one()

 When compiling Lustre without optimization, when using GCOV,
 the lprocfs_stats_alloc_one() symbol is not properly exported to other modules
 and causes the ptlrpc module to fail loading with an unknown symbol.
 Added EXPORT_SYMBOL(lprocfs_stats_alloc_one) so that this works properly.

Seagate-bug-id: MRP-3188
Signed-off-by: Chennaiah Palla <chennaiah.palla@seagate.com>
Change-Id: I8ef02a0e0bf519fa93f85cb162a6340e3feeb736
Reviewed-on: http://review.whamcloud.com/17443
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>