staging: rtl8723bs: Fix camel-case in 'struct rt_firmware_hdr'.

Replace camel-case member names with snake-case names per the linux
kernel coding style guidelines.

Signed-off-by: Quytelda Kahja <quytelda@tamalin.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>