MTP: Sanitize filename provided from MTP host#3

Fix string handling on file name

Bug: 130656917
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: Ic6cf2af860f2c5e40fd176b5f4c6d0edfac79b49