libusb: implement libusb_get_max_alt_packet_size

[aokblast]

Summary

The libusb has a function to calculate the size from given interface,
alt_setting, endpoint. Implementing it by refactoring the calculating
function for libusb_get_max_iso_packet_size.

Sponsored By: FreeBSD Foundation

[aokblast]

Add missing parentheses in return

[aokblast]

Rebase to main and fix potential error

[lwhsu]

lib/libusb/libusb10.c

642

pdconf seems leaked here.

662

for all the early return below, except the if (ret < 0), pdconf needs being free()'d?

[aokblast]

leaks

[lwhsu]

lib/libusb/libusb.3

206

do you mean multiply the multiplier?

[unitrunker_unitrunker.net]

lib/libusb/libusb.3

203

Returns the packet size on success,