crypto: axis - hide an unused variable

Without CONFIG_DEBUG_FS, we get a harmless warning:

drivers/crypto/axis/artpec6_crypto.c:352:23: error: 'dbgfs_root' defined but not used [-Werror=unused-variable]

This moves it into the #ifdef that hides the only user.

Fixes: a21eb94f ("crypto: axis - add ARTPEC-6/7 crypto accelerator driver")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Lars Persson <larper@axis.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/axis/artpec6_crypto.c

@@ -349,8 +349,6 @@ struct artpec6_crypto_aead_req_ctx {
 /* The crypto framework makes it hard to avoid this global. */
 static struct device *artpec6_crypto_dev;
 
-static struct dentry *dbgfs_root;
-
 #ifdef CONFIG_FAULT_INJECTION
 static DECLARE_FAULT_ATTR(artpec6_crypto_fail_status_read);
 static DECLARE_FAULT_ATTR(artpec6_crypto_fail_dma_array_full);
@@ -2984,6 +2982,8 @@ struct dbgfs_u32 {
 	char *desc;
 };
 
+static struct dentry *dbgfs_root;
+
 static void artpec6_crypto_init_debugfs(void)
 {
 	dbgfs_root = debugfs_create_dir("artpec6_crypto", NULL);