ice: convert ice_mbx_clear_malvf to void and use WARN

The ice_mbx_clear_malvf function checks for a few error conditions before
clearing the appropriate data. These error conditions are really warnings
that should never occur in a properly initialized driver. Every caller of
ice_mbx_clear_malvf just prints a dev_dbg message on failure which will
generally be ignored.

Convert this function to void and switch the error return values to
WARN_ON. This will make any potentially misconfiguration more visible and
makes future refactors that involve changing how we store the malicious VF
data easier.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
Tested-by: Marek Szlosek <marek.szlosek@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>