Add required locking around idr_ routines, retry the idr_pre_get/idr_get_new
pair properly, and sprinkle in some likely/unlikely for good measure.

(Lack of idr locking didn't hurt when all callers were I2C clients, as the
i2c-core serialized for us anyway.  Now that we have non I2C hwmon drivers,
this is truly necessary.)
Signed-off-by: Mark M. Hoffman <mhoffman@lightlink.com>
Signed-off-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>