staging: rtl8192e: Remove unused _rtl92e_wx_get_sens function

After removal of rf_set_sens variable, the _rtl92e_wx_get_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/eae80c4e2ac7f386c853cf824135b988c3666031.1682358035.git.yogi.kernel@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>