[crypto] PSA API: remove otPlatCryptoInit API

This commit removes otPlatCryptoInit API and moves responsibility of
initializing the Crypto subsystem to the platform.

Signed-off-by: Łukasz Duda <[email protected]>

src/core/crypto/crypto_platform_mbedtls.cpp

@@ -78,11 +78,6 @@ static constexpr uint16_t kEntropyMinThreshold = 16;
 #endif
 #endif
 
-OT_TOOL_WEAK void otPlatCryptoInit(void)
-{
-    // Intentionally empty.
-}
-
 // AES  Implementation
 OT_TOOL_WEAK otError otPlatCryptoAesInit(otCryptoContext *aContext)
 {

src/core/crypto/crypto_platform_psa.cpp

@@ -200,8 +200,6 @@ exit:
     return error;
 }
 
-OT_TOOL_WEAK void otPlatCryptoInit(void) { psa_crypto_init(); }
-
 OT_TOOL_WEAK otError otPlatCryptoImportKey(otCryptoKeyRef      *aKeyRef,
                                            otCryptoKeyType      aKeyType,
                                            otCryptoKeyAlgorithm aKeyAlgorithm,

src/core/thread/key_manager.cpp

@@ -176,8 +176,6 @@ KeyManager::KeyManager(Instance &aInstance)
     , mKekFrameCounter(0)
     , mIsPskcSet(false)
 {
-    otPlatCryptoInit();
-
 #if OPENTHREAD_CONFIG_PLATFORM_KEY_REFERENCES_ENABLE
     {
         NetworkKey networkKey;