staging/lustre/ptlrpc: Correctly calculate hrp->hrp_nthrs

staging/lustre/ptlrpc: Correctly calculate hrp->hrp_nthrs

cpu_pattern can specify exactly 1 cpu in a partition:
"0[0]". That means CPT0 will have CPU 0. CPU 0 can have
hyperthreading enabled. This combination would result in

weight = cfs_cpu_ht_nsiblings(0);
hrp->hrp_nthrs = cfs_cpt_weight(ptlrpc_hr.hr_cpt_table, i);
hrp->hrp_nthrs /= weight;

evaluating to 0. Where
cfs_cpt_weight(ptlrpc_hr.hr_cpt_table, i) == 1
weight == 2

Therefore, if hrp_nthrs becomes zero, just set it to 1.

Signed-off-by: Amir Shehata <amir.shehata@intel.com>
Reviewed-on: http://review.whamcloud.com/19106
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-8492
Reviewed-by: Liang Zhen <liang.zhen@intel.com>
Reviewed-by: Doug Oucharek <doug.s.oucharek@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>