selftest: tpm2: Add Client.__del__() to close /dev/tpm* handle

stable inclusion
from stable-v5.10.150
commit 278d8ba2b288e8f7928f2333f8611a5f0fdbdd68
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I6D0XA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=278d8ba2b288e8f7928f2333f8611a5f0fdbdd68



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[ Upstream commit 2d869f0b ]

The following output can bee seen when the test is executed:

  test_flush_context (tpm2_tests.SpaceTest) ... \
    /usr/lib64/python3.6/unittest/case.py:605: ResourceWarning: \
    unclosed file <_io.FileIO name='/dev/tpmrm0' mode='rb+' closefd=True>

An instance of Client does not implicitly close /dev/tpm* handle, once it
gets destroyed. Close the file handle in the class destructor
Client.__del__().

Fixes: 6ea3dfe1 ("selftests: add TPM 2.0 tests")
Cc: Shuah Khan <shuah@kernel.org>
Cc: linux-kselftest@vger.kernel.org
Cc: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Jialin Zhang <zhangjialin11@huawei.com>