habanalabs/gaudi: read div_sel value from firmware

Even when running with unsecured f/w, we should read the PLL div_sel
value from the f/w as this register is always privileged.

Signed-off-by: Ohad Sharabi <osharabi@habana.ai>
Reviewed-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Oded Gabbay <ogabbay@kernel.org>