Fix STM32H5 init

Author: multiplemonomials

connectivity/drivers/emac/TARGET_STM/STM32EthMACv2.cpp

@@ -249,14 +249,19 @@ namespace mbed {
         /* Init the low level hardware : GPIO, CLOCK, NVIC. */
         EthInitPinmappings();
 
+
+#ifdef TARGET_STM32H7
         // Use RMII
         HAL_SYSCFG_ETHInterfaceSelect(SYSCFG_ETH_RMII);
 
         /* Dummy read to sync with ETH */
-#ifdef TARGET_STM32H5
-        (void)SBS->PMCR;
-#else
         (void)SYSCFG->PMCR;
+#else
+        __HAL_RCC_SBS_CLK_ENABLE();
+        HAL_SBS_ETHInterfaceSelect(SBS_ETH_RMII);
+
+        /* Dummy read to sync with ETH */
+        (void)SBS->PMCR;
 #endif
 
         /* Ethernet Software reset */

connectivity/drivers/emac/include/GenericEthDMA.h

@@ -310,12 +310,12 @@ namespace mbed {
         size_t rxDescsOwnedByApplication; ///< Number of Rx descriptors owned by the application and needing buffers allocated.
         std::atomic<size_t> rxNextIndex; ///< Index of the next descriptor that the DMA will populate.  Updated by application but used by ISR.
 
-        // Alignment required for Rx memory buffers.  Normally they don't need alignment but
+        // Alignment required for Rx memory buffers.  Normally they don't need more than word alignment but
         // if we are doing cache operations they need to be cache aligned.
 #if __DCACHE_PRESENT
         static constexpr size_t RX_BUFFER_ALIGN = __SCB_DCACHE_LINE_SIZE;
 #else
-        static constexpr size_t RX_BUFFER_ALIGN = 2;
+        static constexpr size_t RX_BUFFER_ALIGN = sizeof(uint32_t);
 #endif
 
         /// Payload size of buffers allocated from the Rx pool.  This is the allocation unit size