By Anirban Sen and Manya Saini(Reuters) - SoftBank Group Corp's Arm Ltd is expected to report a revenue decline of about 1% in the year ended March, when the chip designer reveals its initial public offering (IPO) filing on Monday, according to a person familiar with the matter. Earlier on Friday, Reuters reported that SoftBank had acquired the 25% stake in Arm it did not directly own from its Vision Fund unit in a deal that valued the chip designer at $64 billion. Reuters had previously reported that SoftBank was aiming to list Arm at a valuation of $60 billion to $70 billion in the IPO