Change in flashrom[master]: usbblaster_spi.c: Refactor singleton states into reentrant pattern

[Angel Pons (Code Review)]

Attention is currently required from: Nico Huber, Anastasia Klimchuk.
Angel Pons has posted comments on this change. ( https://review.coreboot.org/c/flashrom/+/54044 )

Change subject: usbblaster_spi.c: Refactor singleton states into reentrant pattern
......................................................................

Patch Set 1: Code-Review+2

(3 comments)

File usbblaster_spi.c:

https://review.coreboot.org/c/flashrom/+/54044/comment/d203e14c_eb4938d8 
PS1, Line 55: 	struct ftdi_context ftdic;
Having a struct with only one member looks odd, but it makes sense for consistency with other programmers.

(No action needed)

https://review.coreboot.org/c/flashrom/+/54044/comment/9275999f_04022c25 
PS1, Line 165: static int usbblaster_shutdown(void *data)
             : {
             : 	free(data);
             : 	return 0;
             : }
> Seems fine to me. […]

Makes sense. This patch changes programmer context storage from a global variable to dynamically-allocated memory, and one needs to free() this memory to avoid memory leaks. Adding a shutdown function to do this is a very reasonable thing to do.

https://review.coreboot.org/c/flashrom/+/54044/comment/c6a69f1c_77219d65 
PS1, Line 185: 	struct ftdi_context ftdic;
We could allocate `usbblaster_data` early and use `usbblaster_data->ftdic` instead of having a second local variable. Can be done in a separate patch.