wifi: rtl8xxxu: Detect the maximum supported channel width

wifi: rtl8xxxu: Detect the maximum supported channel width

Some devices malfunction when connected to a network with 40 MHz channel
width, because they don't support that.

RTL8188FU, RTL8192FU, and RTL8710BU (RTL8188GU) have a way to signal
this (and some other capabilities) to the driver. Get this information
from the hardware and advertise 40 MHz support only when the hardware
can handle it. We assume the other chips can always handle it.

RTL8710BU needs a different way to retrieve this information, which will
be implemented some other time.

Fixes: dbf9b7bb0edf ("wifi: rtl8xxxu: Enable 40 MHz width by default")
Cc: stable@vger.kernel.org
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=221394
Signed-off-by: Bitterblue Smith <rtl8821cerfe2@gmail.com>
Reviewed-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/c57de68e-5d57-4c26-898f-8a284bb25381@gmail.com