Add legacy fallback for midi device identification

This commit refines the MIDI device identification logic to prioritize a new sysfs-based method that relies on the udc sysfs interface. If this method fails to identify the MIDI device (e.g., on older kernels lacking the necessary udc sysfs entries), the code falls back to the legacy method using the android_usb sysfs interface.

This ensures compatibility with vendor freeze devices running older kernels while still leveraging the improved sysfs-based approach when available.

Change-Id: I60d139b6aee2cfd7cf3cdea5fc8f1dc46f85cfca
Flag: android.hardware.usb.flags.enable_usb_sysfs_midi_identification
Bug: 333778731
Test: exercise usb midi with the flag on/off