[nrf noup] tests: crypto: Set size for PSA slot

noup since this option does not exist upstream.

The Oberon PSA core has an option to manually set
the buffer size of the PSA key slots in bytes.

This option here:
MBEDTLS_PSA_STATIC_KEY_SLOT_BUFFER_SIZE

This option has a default value of 16 since it
directly affects the memory usage.

The crypto tests use a secp256r1 key and thus since
the public key for this key is 65 bytes long we need
to set the option in the sample.

Signed-off-by: Georgios Vasilakis <[email protected]>
(cherry picked from commit 2da4861)

Author: Vge0rge

tests/crypto/secp256r1/mbedtls.conf

@@ -1,6 +1,7 @@
 CONFIG_MBEDTLS=y
 CONFIG_MBEDTLS_PSA_CRYPTO_C=y
 CONFIG_MBEDTLS_PSA_P256M_DRIVER_ENABLED=y
+CONFIG_MBEDTLS_PSA_STATIC_KEY_SLOT_BUFFER_SIZE=65
 CONFIG_MBEDTLS_PSA_STATIC_KEY_SLOTS=y
 CONFIG_MBEDTLS_PSA_KEY_SLOT_COUNT=2