lib: rsa: cosmetic: fix building warning

add initialization of variable 'node',this can aviod the building
warning:

    'node' may be used uninitialized [-Wmaybe-uninitialized]

Signed-off-by: Haijun Qin <qinhaijun@eswincomputing.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/lib/rsa/rsa-sign.c b/lib/rsa/rsa-sign.c
index b2a2119..d20bdb5 100644
--- a/lib/rsa/rsa-sign.c
+++ b/lib/rsa/rsa-sign.c
@@ -608,7 +608,7 @@
 	BIGNUM *modulus, *r_squared;
 	uint64_t exponent;
 	uint32_t n0_inv;
-	int parent, node;
+	int parent, node = -FDT_ERR_NOTFOUND;
 	char name[100];
 	int ret;
 	int bits;