bootutil : Move fake_rng declaration

Signed-off-by: Raphael Dupont <raphael7dup@gmail.com>

boot/bootutil/src/encrypted_priv.h

@@ -36,7 +36,6 @@
 
 #if defined(MCUBOOT_ENCRYPT_RSA)
 #    define EXPECTED_ENC_TLV    IMAGE_TLV_ENC_RSA2048
-int fake_rng(void *p_rng, unsigned char *output, size_t len);
 #elif defined(MCUBOOT_ENCRYPT_KW)
 #    define EXPECTED_ENC_TLV    IMAGE_TLV_ENC_KW
 #elif defined(MCUBOOT_ENCRYPT_EC256)
@@ -61,6 +60,12 @@ _Static_assert(EC_CIPHERKEY_INDEX + BOOT_ENC_KEY_SIZE == EXPECTED_ENC_LEN,
 #include "bootutil/crypto/ecdh_x25519.h"
 #endif
 
+#if defined(MCUBOOT_ENCRYPT_RSA)
+
+int fake_rng(void *p_rng, unsigned char *output, size_t len);
+
+#endif /* MCUBOOT_ENCRYPT_RSA */
+
 #if defined(MCUBOOT_ENCRYPT_EC256) || defined(MCUBOOT_ENCRYPT_X25519)
 
 int expand_secret(uint8_t *derived_key, uint8_t *shared);