Turbotax was updated to allow the deduction for mortgage insurance premiums as of February 22, 2018. It's included in the entry for mortgage interest.
Remember that the usual rules still apply: there are income limits, and pre-paid lump sum amounts must be spread out over 84 months, you can only deduct the number of months worth that you paid in 2017. (Up front lump sum amounts for the VA funding fee and Rural Housing Authority are fully deductible, and monthly premiums are fully deductible.)
Also, because the deduction expired at the end of 2016 and was not renewed until 2018, many banks did not report mortgage insurance on their 1098 forms. If you don't know your PMI or MIP amount, contact your mortgage lender.