add tests to verify IFS (In Field Scan) driver functionality

To verify IFS (In Field Scan [1]) driver functionality, add the following 6
test cases:
  1. Verify that IFS sysfs entries are created after loading the IFS module
  2. Check if loading an invalid IFS test image fails and loading a valid
     one succeeds
  3. Perform IFS scan test on each CPU using all the available image files
  4. Perform IFS scan with first test image file on a random CPU for 3
     rounds
  5. Perform IFS ARRAY BIST(Board Integrated System Test) test on each CPU
  6. Perform IFS ARRAY BIST test on a random CPU for 3 rounds

These are not exhaustive, but some minimal test runs to check various
parts of the driver. Some negative tests are also included.

[1] https://docs.kernel.org/arch/x86/ifs.html

Pengfei Xu (4):
  selftests: ifs: verify test interfaces are created by the driver
  selftests: ifs: verify test image loading functionality
  selftests: ifs: verify IFS scan test functionality
  selftests: ifs: verify IFS ARRAY BIST functionality

 MAINTAINERS                                   |   1 +
 tools/testing/selftests/Makefile              |   1 +
 .../drivers/platform/x86/intel/ifs/Makefile   |   6 +
 .../platform/x86/intel/ifs/test_ifs.sh        | 494 ++++++++++++++++++
 4 files changed, 502 insertions(+)
 create mode 100644 tools/testing/selftests/drivers/platform/x86/intel/ifs/Makefile
 create mode 100755 tools/testing/selftests/drivers/platform/x86/intel/ifs/test_ifs.sh

---
Changes:
v1 to v2:
  - Rebase to v6.10 cycle kernel and resolve some code conflicts
  - Improved checking of IFS ARRAY_BIST support by leveraging sysfs entry
    methods (suggested by Ashok)

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2.43.0