Chicago radio legend Steve Dahl has kept active through four tumultuous decades in the broadcasting business, and he’s not expecting prostate cancer to slow him down.“I have a curable cancer that 1 in 8 men will be diagnosed with, so this isn’t a pity party,” he told the Sun-Times in an email.The host known for his humor and candor revealed the diagnosis Saturday on social media. Since a biopsy detected the cancer a year ago, he’s had an MRI for…