Mount ptp separately from mtp

Ptp is now mounted in its own directory so the
mtp endpoint does not need to be closed to write
the ptp descriptors.

sys.usb.ffs.mtp.ready is also now not needed.

Bug: 72877174
Test: switch config to mtp/ptp

Change-Id: Ib81b63831f8898ddd9f73848b77b7c83edce4d11
1 file changed