wifi: rtlwifi: rtl_usb: Store the endpoint addresses

And use the stored addresses in rtl8192cu instead of hardcoding them.

This is what the vendor drivers do.

Perhaps this is not strictly necessary for RTL8192CU devices. However,
the dual mac version of RTL8192DU has two USB interfaces, each with its
own set of endpoints. Hardcoding their addresses in the upcoming
rtl8192du driver would require making some assumptions which I'm not
qualified to make.

Signed-off-by: Bitterblue Smith <rtl8821cerfe2@gmail.com>
Acked-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://msgid.link/7b6a602a-6101-4bab-958d-bcff4d565b40@gmail.com