spmi: pmic-arb: clean up pmic_arb_find_apid function

Clean up the pmic_arb_find_apid() by using the local
variables to improve the code readability.

Signed-off-by: Kiran Gunda <kgunda@codeaurora.org>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>