Change in flashrom[master]: tests: Mock file i/o for linux_mtd and linux_spi tests

[Anastasia Klimchuk (Code Review)]

Attention is currently required from: Nico Huber, Edward O'Callaghan, Angel Pons.
Anastasia Klimchuk has posted comments on this change. ( https://review.coreboot.org/c/flashrom/+/56413 )

Change subject: tests: Mock file i/o for linux_mtd and linux_spi tests
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Patch Set 7:

(1 comment)

File tests/init_shutdown.c:

https://review.coreboot.org/c/flashrom/+/56413/comment/081654ca_00c603fc 
PS6, Line 237: 			return strlen(entry.data);
> Hmmm, now that I take a look at this again: […]

I added `strlen(entry.data) + 1`.
For the 6 paths that are mocked in this test (type/name etc) size is always 1 and len is always sizeof(buf), and buf has enough capacity. Do you mean to assert that the value written into buf is not larger than size*len ?