qcacmn: Resolve compilation errors in lower version kernels

symmetric key cipher APIs are present in linux kernel version 4.3
and above only.

Add changes to protect symmetric key cipher APIs invoke in lower
version kernels.

Change-Id: I512d0d98886c887a242a834763b46b2ec0cd4751
CRs-Fixed: 2034502

qdf/linux/src/qdf_crypto.c

@@ -261,6 +261,7 @@ error:
 	return ret;
 }
 
+#if (LINUX_VERSION_CODE >= KERNEL_VERSION(4, 3, 0))
 int qdf_aes_ctr(const uint8_t *key, unsigned int key_len, uint8_t *siv,
 		const uint8_t *src, size_t src_len, uint8_t *dest, bool enc)
 {
@@ -319,3 +320,10 @@ int qdf_aes_ctr(const uint8_t *key, unsigned int key_len, uint8_t *siv,
 	crypto_free_skcipher(tfm);
 	return ret;
 }
+#else
+int qdf_aes_ctr(const uint8_t *key, unsigned int key_len, uint8_t *siv,
+		const uint8_t *src, size_t src_len, uint8_t *dest, bool enc)
+{
+	return -EINVAL;
+}
+#endif