[PATCH] iwlwifi: add read rate scale table debugfs function

This patch adds read rate scale table debugfs function for 4965
rate scaling module.

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>