hwmon: (adt7475) Make adt7475_read_word() return errors

[ Upstream commit f196dec6d50abb2e65fb54a0621b2f1b4d922995 ]

The adt7475_read_word() function was meant to return negative error
codes on failure.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Tokunori Ikegami <ikegami@allied-telesis.co.jp>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>