rtc: isl12022: simplify some expressions

rtc: isl12022: simplify some expressions

These instances of '&client->dev' might as well be spelled 'dev', since
'client' has been computed from 'dev' via 'client =
to_i2c_client(dev)'.

Later patches will get rid of that local variable 'client', so remove
these unnecessary references so those later patches become easier to
read.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Link: https://lore.kernel.org/r/20220921114624.3250848-5-linux@rasmusvillemoes.dk
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>