[PATCH] iwlwifi: removing unnecessary memset in 4965 rate scale

This patch removes redundant memset in rate scale. In rs_alloc_sta,
kzalloc is used so the memset can be avoided. In rs_rate_init, it is
a bug fix since it overrides everything set in other handlers namely
add_debugfs.

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>