gigaset: use dev_ macros for messages

gigaset: use dev_ macros for messages

The info() / warn() / err() macros from usb.h for generating kernel
messages are considered inferior to dev_info() / dev_warn() / dev_err()
from device.h.  Replace them where possible.  Also correct the severity
level and improve the text of one message.

Signed-off-by: Tilman Schmidt <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>