platform_mbed.h: Fix and align EXPERIMENTAL_API check

Some of the lines in `platform_mbed.h` only have `FEATURE_PSA`
checked, which is always set for Mbed OS PSA targets but the PSA
APIs are not actually available unless `FEATURE_EXPERIMENTAL_API`
is also enabled. To fix this and improve readability, group all
PSA-related lines and check both macros.

Author: LDong-Arm

connectivity/mbedtls/platform/inc/platform_mbed.h

@@ -21,7 +21,9 @@
 #ifndef __PLATFORM_MBED__H__
 #define __PLATFORM_MBED__H__
 
-#if (defined(FEATURE_EXPERIMENTAL_API) && defined(FEATURE_PSA) && defined(MBEDTLS_ENTROPY_NV_SEED))
+#if defined(FEATURE_EXPERIMENTAL_API) && defined(FEATURE_PSA)
+
+#if defined(MBEDTLS_ENTROPY_NV_SEED)
 
 #include "default_random_seed.h"
 
@@ -37,19 +39,8 @@
  * MBEDTLS_ENTROPY_NV_SEED is enabled. */
 #define MBEDTLS_PSA_INJECT_ENTROPY
 
-#endif  // (defined(FEATURE_PSA) && defined(MBEDTLS_ENTROPY_NV_SEED))
-
-#if DEVICE_TRNG
-#if !defined(MBEDTLS_ENTROPY_HARDWARE_ALT)
-#define MBEDTLS_ENTROPY_HARDWARE_ALT
-#endif
-#endif
-
-#if defined(MBEDTLS_CONFIG_HW_SUPPORT)
-#include "mbedtls_device.h"
-#endif
+#endif // defined(MBEDTLS_ENTROPY_NV_SEED)
 
-#if defined(FEATURE_PSA)
 /* The following configurations are a needed for Mbed Crypto submodule.
  * They are related to the persistent key storage feature.
  */
@@ -58,6 +49,17 @@
 #undef MBEDTLS_PSA_CRYPTO_STORAGE_FILE_C
 
 #define MBEDTLS_ENTROPY_HARDWARE_ALT
+
+#endif  // defined(FEATURE_EXPERIMENTAL_API) && defined(FEATURE_PSA)
+
+#if DEVICE_TRNG
+#if !defined(MBEDTLS_ENTROPY_HARDWARE_ALT)
+#define MBEDTLS_ENTROPY_HARDWARE_ALT
+#endif
+#endif
+
+#if defined(MBEDTLS_CONFIG_HW_SUPPORT)
+#include "mbedtls_device.h"
 #endif
 
 /*