provisioning: Add troubleshooting to README

It is a common source of failure that the provisioning data is
overwritten when programming a new flash image. In a new troubleshooting
section in the README, add a recommendation to upgrade the DAPLink
version to a version that supports partial image updates.

Author: Patater

provisioning/README.md

@@ -69,3 +69,13 @@ To generate a key, specify the lifetime with `psa_set_key_lifetime()` and
 This example generates certificate signing requests (CSRs) which can be used
 for TLS client authentication. The CSR is printed over the serial port, for
 use with your certificate authority (CA).
+
+
+### Troubleshooting
+
+If your provisioning data isn't persisting, there is a chance it is being
+overwritten by the flash programmer. If using DAPLink, ensure you are using a
+DAPLink interface version of 0246 or newer. Older versions of DAPLink do not
+support partial flash programming, and always overwrite any data stored in
+internal flash. In our case, this would be the provisioning data we want to
+keep!