MTP: Sanitize filename provided from MTP host#2

Fix potential stack buffer-overflow

Bug: 135764253
Test: atest frameworks/av/media/mtp/tests
Test: Manual test: modified libmtp for long path traversal attack
Test: Manual test: normal recursive folder copy
Change-Id: Idcefb9a27da7481e821f3de22821cb461e2e1a9b