test(mbedtls): fix in-place AES-CTR PSRAM test on targets without AES hardware

With MBEDTLS_PSA_ASSUME_EXCLUSIVE_BUFFERS enabled, an in-place
psa_cipher_update() reaches the selected cipher implementation without
defensive buffer copies. The ESP AES PSA driver accepts an in-place
update of any length for CTR (PSA classifies CTR as a stream cipher, so
the driver's block_length is 1), but on targets without the AES
peripheral (e.g. ESP32-C61) the operation falls back to the mbedtls
builtin cipher layer, which rejects in-place updates whose length is
not a multiple of the block size (MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
surfacing as PSA_ERROR_INVALID_ARGUMENT).

Round the in-place test length down to a block multiple when
CONFIG_MBEDTLS_HARDWARE_AES is not set; partial-block PSRAM coverage is
retained through the separate-buffer alignment tests.

components/mbedtls/test_apps/mbedtls_ut/main/test_psa_aes.c

@@ -1952,7 +1952,11 @@ void aes_psram_one_buf_ctr_test(void)
     uint8_t nonce[16];
     uint8_t key[16];
     psa_status_t status;
+#if CONFIG_MBEDTLS_HARDWARE_AES
     size_t SZ = TEST_AES_CTR_DATA_LEN;
+#else
+    size_t SZ = TEST_AES_CTR_DATA_LEN - (TEST_AES_CTR_DATA_LEN % 16);
+#endif
     size_t ALIGNMENT_SIZE_BYTES = 32;
     memset(nonce, 0x2F, 16);
     memset(key, 0x1E, 16);