serial_usb: supporting multiple instance

[sam0737]

Hi,

I have patched the HAL serial_usb to support multiple serial_usb instance.

https://github.com/sam0737/chibios-rt-a ... c3300c5430

There is no breaking change to the user interface (old code should work as is), the changes are:
* remove the dependency from usbp->param
* User wishing to use multiple instance should specify the interrupt, tx, rx EP number in SerialUSBConfig
* An linked list is added to check/map the EP number of USB/Queue hooks to the device instance

I hope the patch is useful =)

[Giovanni]

Hi,

Thanks for the patch however a fix for this problem has been committed last week

Looking at your code I realized that I didn't think to separate line coding, I will merge at least that part.

Giovanni