By John Cross Erling Haaland scored five for rampant Manchester City and then warned: “We’re coming.” Reigning champions City smashed Luton as Pep Guardiola’s men eye another Treble after cruising into the FA cup quarter-final. Kevin De Bruyne provided assists for four of Haaland’s five goals as the City striker took his tally to 27 goals this season. City’s only downside was Jack Grealish suffering a recurrence of his groin injury which forced him off after just 38 minutes and will be a major worry for England ahead of this summer’s Euros. Fit-again Haaland, who last scored five for City in M…