nrfx: fix errata7 workaround in nrfx_nvmc_uicr_word_read/write

[campbellyoung]

The errata 7 workaround is broken in the current state, and it causes issues with NRF Connect SDK 3.2.1.

Symptom: if I read UICR via TF-M, the actual read works fine, but the next time I generate a panic, it will HardFault instead of being handled properly.

I'm not sure specifically WHY this happens, but this patch fixes it, and seems more logically consistent with the actual errata.

Root issue:

NRF_ERRATA_DYNAMIC_CHECK does a flash read in nrf91_errata_7 ( when it checks NRF_FICR_S) which happens before the actual memory barrier executes.

Pull requests are a little annoying with all the different repos, so I've done the PR here and added a working sample to reproduce the issue below, hope that's fine.

https://github.com/campbellyoung/sdk-nrf/blob/tfm-uicr-panic/samples/crypto/tfm_uicr_panic/

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[nika-nordic]

hi @campbellyoung ,

thanks for reporting this. We will look into the issue internally and come back to you