staging: r8188eu: limit rtw_wx_read_rf to path a

staging: r8188eu: limit rtw_wx_read_rf to path a

Commit 3b011b097c38 ("staging: r8188eu: limit rf register writes to
path a") limits rf register writes by private ioctls to RF_PATH_A.
Apart from private ioctls, the rest of the driver uses only path a.

This patch limits rf register reads by the private ioctl 0x0D, which
calls rtw_wx_read_rf, to path a.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20220212161737.381841-7-martin@kaiser.cx
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>