[SCSI] qla2xxx: Basic infrastructure for dynamic logging.

This patch adds the dynamic logging framework to the qla2xxx driver.
The user will be able to change the logging levels on the fly i.e.
without load/unload of the driver. This also enables logging to be
enabled for a particular section of the driver such as initialization,
device discovery etc.

Signed-off-by: Saurav Kashyap <saurav.kashyap@qlogic.com>
Signed-off-by: Giridhar Malavali <giridhar.malavali@qlogic.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>