rsi: Add usb multi-byte read operation

USB multibyte read will be used in the new firmware loading method
for RS9113 chipset.

Signed-off-by: Prameela Rani Garnepudi <prameela.j04cs@gmail.com>
Signed-off-by: Amitkumar Karwar <amit.karwar@redpinesignals.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>