dm: core: Add functions to read 64-bit dt properties

This patch adds functions dev_read_u64_default & dev_read_u64
to read unsigned 64-bit values from devicetree.

Signed-off-by: T Karthik Reddy <t.karthik.reddy@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

drivers/core/ofnode.c

@@ -79,7 +79,7 @@ int ofnode_read_u64(ofnode node, const char *propname, u64 *outp)
 	return 0;
 }
 
-int ofnode_read_u64_default(ofnode node, const char *propname, u64 def)
+u64 ofnode_read_u64_default(ofnode node, const char *propname, u64 def)
 {
 	assert(ofnode_valid(node));
 	ofnode_read_u64(node, propname, &def);