clk: bcm2835: fix bcm2835_clock_choose_div

clk: bcm2835: fix bcm2835_clock_choose_div

The commit d4ba1003995c ("clk: bcm2835: Remove unused variable")
accidentially breaks the behavior of bcm2835_clock_choose_div() and
booting of Raspberry Pi. The removed do_div macro call had side effects,
so we need to restore it.

Fixes: d4ba1003995c ("clk: bcm2835: Remove unused variable")
Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Link: https://lore.kernel.org/r/20220428183010.1635248-1-stefan.wahren@i2se.com
Tested-by: Maxime Ripard <maxime@cerno.tech>
Acked-by: Maxime Ripard <maxime@cerno.tech>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>