By Arasu Kannagi Basil Feb 24 (Reuters) - Medtronic's MiniMed Group said on Tuesday it was targeting up to $7.86 billion valuation in its U.S. initial public ‌offering, marking a step forward in the medical device maker's plan to ‌separate its diabetes business. The Northridge, California-based unit, a heavyweight in diabetes care and which makes products such ​as insulin pumps, glucose monitoring systems and sensors, is seeking to raise up to $784 million in its IPO by offering 28 million shares priced ...