audioflinger: fire routing changed to mmap clients before creating patch

For mmap streams, they will be disconnected and the client is required
to reopen the stream when the routing is changed. In that case, it is
safe to fire the routing changed to mmap clients before patch creation
arrive the HAL.

Bug: 325129412
Test: Test disconnect with OboeTester
Test: Connect/Disconnect USB device with DrumThumper
Change-Id: Icfd9e93a81bb28b427a95f4dc1fa565b5f98e1a4