Looking at the ACGME website, neurology PGY1 year requirements include six months of IM and an additional two months in IM, EM, FM, or peds. This is the minimum; as an intern, I personally did ~10 months of inpatient medicine and neurology, including 2 months of ICU, as well as a few weeks of emergency medicine.
Anecdotally, I know someone who switched from IM -> neurology after PGY1 year. His neuro program made him repeat a (modified) intern year.
I don't know for certain, but I feel fairly confident in saying no program would take a PGY1 psychiatry resident as a PGY2. Neuro residents are expected to be able to handle general inpatient IM issues without assistance; do you think you can do that after your intern year?
All the same, I'd say go for it if you're interested. Your psych training won't go to waste, and you probably won't have to repeat a psych month as a neurology resident.