bnxt_en: Suppress error messages when querying DSCP DCB capabilities.

Some firmware versions do not support this so use the silent variant
to send the message to firmware to suppress the harmless error.  This
error message is unnecessarily alarming the user.

Fixes: afdc8a84

 ("bnxt_en: Add DCBNL DSCP application protocol support.")
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>