lsusb: return on short bLength in the class-specific descriptor dispatchers

The audio/video/MIDI/DFU class-specific descriptor dump entry points all
share a "warn but fall through" pattern on a too-short bLength:

	if (buf[1] != USB_DT_CS_INTERFACE)
		printf("      Warning: Invalid descriptor\n");
	else if (buf[0] < 3)
		printf("      Warning: Descriptor too short\n");
	... desc_dump(dev, table, buf + 3, buf[0] - 3, indent);

so a bLength of 2 underflows buf[0]-3 to UINT_MAX as the buf_len handed
to desc_dump() (or dump_bytes() in the unknown-subtype tails), defeating
every per-field bounds check in the engine.  The "else" makes it worse:
the caller's switch on bDescriptorType falls CS_DEVICE through to
CS_INTERFACE, so a buf[1]==0x21 takes the "Invalid descriptor" arm and
skips the length check entirely.

Make every dispatcher's short-descriptor check independent of the type
check and return after the warning.  Covers dump_audiocontrol_interface,
dump_audiostreaming_interface, dump_audiostreaming_endpoint (which had
no length check at all), dump_midistreaming_interface/_endpoint,
dump_videocontrol_interface, dump_videocontrol_interrupt_endpoint,
dump_videostreaming_interface, dump_dfu_interface, and
dump_comm_descriptor (which opened with switch(buf[2]) before any length
check at all, so a 2-byte CDC descriptor read the subtype byte one past
libusb's extra[] allocation).

Assisted-by: gkh_clanker_t1000
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>