wifi: rtw89: Add usb.{c,h}

JIRA: https://issues.redhat.com/browse/RHEL-114889

commit 2135c28
Author: Bitterblue Smith <rtl8821cerfe2@gmail.com>
Date:   Mon Jun 30 23:46:55 2025 +0300

    wifi: rtw89: Add usb.{c,h}
    
    Add basic USB support. No TX/RX aggregation, no switching to USB 3 mode.
    
    RTL8851BU and RTL8832BU work.
    
    Signed-off-by: Bitterblue Smith <rtl8821cerfe2@gmail.com>
    Acked-by: Ping-Ke Shih <pkshih@realtek.com>
    Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
    Link: https://patch.msgid.link/f9ad1664-2d63-4a8f-88bf-c7b7bececbfe@gmail.com

Signed-off-by: Jose Ignacio Tornos Martinez <jtornosm@redhat.com>

Author: jtornosm