selftests: ifs: verify test interfaces are created by the driver

IFS (In Field Scan) driver exposes its functionality via sysfs interfaces.
Applications prepare and exercise the tests by interacting with the
aforementioned sysfs files.

Verify that the necessary sysfs entries are created after loading the IFS
driver.

Initialize test variables needed for building subsequent kself-test cases.

Reviewed-by: Jithu Joseph <jithu.joseph@intel.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Co-developed-by: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Pengfei Xu <pengfei.xu@intel.com>
Acked-by: Jithu Joseph <jithu.joseph@intel.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>