staging: rtl8192e: Remove unused _rtl92e_wx_set_sens function

staging: rtl8192e: Remove unused _rtl92e_wx_set_sens function

After removal of rf_set_sens variable, the _rtl92e_wx_set_sens function
always returns an error code.
This commit removes the unused function and the respective ioctl.

Suggested-by: Philipp Hortmann <philipp.g.hortmann@gmail.com>
Signed-off-by: Yogesh Hegde <yogi.kernel@gmail.com>
Tested-by: Philipp Hortmann <philipp.g.hortmann@gmail.com>
Link: https://lore.kernel.org/r/439386d2940fe70ec2092e87211df5e7946aab82.1682358035.git.yogi.kernel@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>