psa_crypto.c: Fix ifdefs to avoid build warning

[aescolar]

Description

Add a couple of missing ifdefs to avoid having unreachable code with AT_LEAST_ONE_BUILTIN_KDF not defined, which otherwise causes a build warning with clang.

PR checklist

• changelog not required because: Just a build warning fix
• framework PR not required
• mbedtls development PR not required because: no changes
• mbedtls 3.6 PR provided: [3.6] psa_crypto.c: Fix ifdefs to avoid build warning mbedtls#10679
• tf-psa-crypto 1.1 PR provided [1.1] psa_crypto.c: Fix ifdefs to avoid build warning #741
• tests: not required: no new code to be tested

[valeriosetti]

Adding some relevant details for the 2nd reviewer.

This is the PR in the Zephyr fork of TF-PSA-Crypto repo:
zephyrproject-rtos#2

This is the main Zephyr PR with a command on how to reproduce the issue:
zephyrproject-rtos/zephyr#105990

This is the log of the failure:
build.log

[valeriosetti]

LGTM, thanks!

[mpg]

• mbedtls 3.6 PR not required because: no changes

Really? I'm seeing the same function with the same structure in 3.6. Why wouldn't we want to backport those changes?

[mpg]

I'm applying "needs-backport" not as a way to insist this needs backports, but if it doesn't need backports, I think it needs a better justification why.

[valeriosetti]

@mpg I've added backport PRs:

• mbedtls 3.6: [3.6] psa_crypto.c: Fix ifdefs to avoid build warning mbedtls#10679
• tf-psa-crypto 1.1: [1.1] psa_crypto.c: Fix ifdefs to avoid build warning #741

Minor note: I think we should add the tf-psa-crypto 1.1 PR in the description message template, isn't it? In case the answer to this is "yes" then here it is: #742

[valeriosetti]

@mpg I've also added you as reviewer for this PR because I'm doing the backports and I cannot self-approve PRs