staging: r8188eu: move struct rt_firmware_hdr to rtw_fw.h

The structure rt_firmware_hdr is firmware related. Move it to the
rtw_fw.h header.

Signed-off-by: Michael Straube <straube.linux@gmail.com>
Link: https://lore.kernel.org/r/20220202075051.21266-1-straube.linux@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>