staging: rtl8192u: remove unused ieee80211_SignalStrengthTranslate function

clang with W=1 reports
drivers/staging/rtl8192u/ieee80211/ieee80211_rx.c:1961:18: error: unused
  function 'ieee80211_SignalStrengthTranslate' [-Werror,-Wunused-function]
static inline u8 ieee80211_SignalStrengthTranslate(
                 ^
This function is not used so remove it.
It may have been used in the past but that has been commented out.
Also remove the comment.

Signed-off-by: Tom Rix <trix@redhat.com>
Link: https://lore.kernel.org/r/20230323165931.2634587-1-trix@redhat.com


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