tests: Add unit test to run init/shutdown for linux_spi.c

The current implementation tests a particular path of the init
procedure. There are two ways for it to succeed: reading the buffer
size from sysfs and the fallback to getpagesize(). This test does
the latter (fallback to getpagesize).

Extract from meson-logs/testlog.txt for new test:

[ RUN      ] linux_spi_init_and_shutdown_test_success
Testing programmer_init for programmer=25 ...
__wrap_open64 is called
__wrap_ioctl is called
__wrap_ioctl is called
__wrap_ioctl is called
__wrap_fopen64 is called
... programmer_init for programmer=25 successful
Testing programmer_shutdown for programmer=25 ...
... programmer_shutdown for programmer=25 successful
[       OK ] linux_spi_init_and_shutdown_test_success

TEST=builds and ninja test

Change-Id: I4911fbb6f04371283f0e62d2196bdd691a227584
Signed-off-by: Anastasia Klimchuk <aklm@chromium.org>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/52498
Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
4 files changed