power: supply: cros_usbpd: remove unused pointer 'dev'

Pointer 'dev' is being assigned but is never used hence it is
redundant and can be removed.

Cleans up clang warning:
variable 'dev' set but not used [-Wunused-but-set-variable]

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>