staging: r8188eu: remove HW_VAR_MLME_SITESURVEY from SetHwReg8188EU()

staging: r8188eu: remove HW_VAR_MLME_SITESURVEY from SetHwReg8188EU()

Remove the HW_VAR_MLME_SITESURVEY case from SetHwReg8188EU() and move
the functionality to two new functions in rtw_mlme_ext.c. This is part
of the ongoing effort to get rid of SetHwReg8188EU().

Tested-by: Philipp Hortmann <philipp.g.hortmann@gmail.com> # Edimax N150
Signed-off-by: Michael Straube <straube.linux@gmail.com>
Link: https://lore.kernel.org/r/20220711174417.10721-1-straube.linux@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>