serial_i2c app: added cmd errors
serial_i2c app: added cmd errors

pdg137/wixel-sdk,markncooper/burnerlight,jamorham/wixel-xDrip,StephenBlackWasAlreadyTaken/wixel-xDrip,StephenBlackWasAlreadyTaken/wixel-xDrip,jamorham/wixel-xDrip,sm6xmm/wixel-xDrip,markncooper/burnerlight,attackcrow/wixel,novagannas/wixel-xDrip,attackcrow/wixel,sm6xmm/wixel-xDrip,saercnap/wixel-DexDrip,Cagier/wixel-xDrip,jamorham/wixel-xDrip,novagannas/wixel-xDrip,attackcrow/wixel,raduiliescu/wixel-DexDrip,kevinwchang/wixel-sdk,sm6xmm/wixel-xDrip,sm6xmm/wixel-xDrip,StephenBlackWasAlreadyTaken/wixel-xDrip,markncooper/burnerlight,raduiliescu/wixel-DexDrip,pdg137/wixel-sdk,novagannas/wixel-xDrip,Cagier/wixel-xDrip,Cagier/wixel-xDrip,raduiliescu/wixel-DexDrip,kevinwchang/wixel-sdk,saercnap/wixel-DexDrip,jamorham/wixel-xDrip,pdg137/wixel-sdk,attackcrow/wixel,kevinwchang/wixel-sdk,saercnap/wixel-DexDrip