rsi: Register interrupt handler before firmware load

Before firmware load, sometimes false interrupts are received.
System hang is observed if interrupt handler is not registered
to receive these interrupts. Hence interrupt handler registration
is moved before firmware load. We will drop these false interrupts
as these are not from the device.

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>