Nikkei drops on weak U.S. data, investors eye earnings next week

* Nikkei had been nearly flat the past four days * AMD's dismal earnings hit chip-related stocks * McDonald's falls to over 7-week low * BOJ bought 36.5 bln yen of ETFs on Thurs By Ayai Tomisawa TOKYO, April 17 (Reuters) - Japan's Nikkei share average dropped on Friday morning after weaker-than-expected U.S. housing data soured the mood, while investors awaited Japanese corporate earnings starting next week. Also dampening sentiment was weakness in Europe shares and conc