ice: return correct error code from ice_aq_sw_rules

Return ICE_ERR_DOES_NOT_EXIST return code if admin command error code is
ICE_AQ_RC_ENOENT (not exist). ice_aq_sw_rules is used when switch
rule is getting added/deleted/updated. In case of delete/update
switch rule, admin command can return ICE_AQ_RC_ENOENT error code
if such rule does not exist, hence return ICE_ERR_DOES_NOT_EXIST error
code from ice_aq_sw_rule, so that caller of this function can decide
how to handle ICE_ERR_DOES_NOT_EXIST.

Signed-off-by: Kiran Patil <kiran.patil@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>