power: supply: bq27xxx: adjust whitespace and use BIT() for bitflags

BIT() is a preferred way to toggle bit-like flags: no problems with 32/64
bit systems, less chances for mistakes.  Remove also unneeded
whitespace.

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>