[M] Change in flashrom[master]: ch341a_spi: Refactor singleton states into reentrant pattern

[Anastasia Klimchuk (Code Review)]

Attention is currently required from: Edward O'Callaghan, Alexander Goncharov.

Anastasia Klimchuk has posted comments on this change. ( https://review.coreboot.org/c/flashrom/+/72807 )

Change subject: ch341a_spi: Refactor singleton states into reentrant pattern
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Patch Set 3:

(2 comments)

File ch341a_spi.c:

https://review.coreboot.org/c/flashrom/+/72807/comment/a5cae2ad_fd65947a 
PS3, Line 80: 	struct libusb_transfer *transfer_out;
            : 	struct libusb_transfer *transfer_ins[USB_IN_TRANSFERS];
            : 
            : 	/* Accumulate delays to be plucked between CS deassertion and CS assertions. */
            : 	unsigned int stored_delay_us;
            : 
            : 	struct libusb_device_handle *handle;
Will default values for these be the same as before?
If not, they should be set in init function. Although 0s and NULLs are probably default initialisation anyway?

https://review.coreboot.org/c/flashrom/+/72807/comment/480477a4_b99f4a94 
PS3, Line 461: msg_pwarn("Cannot detach the existing USB driver. Claiming the interface may fail. %s\n",
             : 			libusb_error_name(ret));
Is this an error branch? It should `goto free_data` then. Or maybe `goto close_handle` ?