flash/nor: Change missing protect_check message from WARN to Info.

flash/nor: Change missing protect_check message from WARN to Info.

Change the current message when a flash driver does not implement
the protect_check function to LOG_INFO() from LOG_WARNING(). The
user is still notified that the procedure isn't available, but
changes the tone to indicate this is expected with this flash
driver and not something that necessarily is a problem to fix.

Change-Id: If8a2e86a23c852d562346ca36734e5d02df4a851
Signed-off-by: Edward Fewell <efewell@ti.com>
Reviewed-on: http://openocd.zylin.com/5539
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>
Tested-by: jenkins
Reviewed-by: Tomas Vanek <vanekt@fbl.cz>