samples: tfm_integration: docs: Fix incorrect sample name

The README.rst in `samples/tfm_integration/tfm_ipc` was incorrectly
referring to `psa_level_1`. README.rst has been updated to refer to
`tfm_ipc` example.

Signed-off-by: Devaraj Ranganna <devaraj.ranganna@linaro.org>
1 file changed