power: supply: cpcap-battery: Simplify coulomb counter calculation with div_s64

We can simplify cpcap_battery_cc_raw_div() with div_s64.

Cc: Merlijn Wajer <merlijn@wizzup.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>