fix: clang-tidy of clang 15 failure due to var naming

Rename variable 'root_offset', as it looked logically correct, to avoid
issue reported by clang-tidy in call to function
'fdt_appendprop_addrrange'.
Clang-tidy was hinting that previous naming suggested variable had
been swapped with third argument of the referred function.

Signed-off-by: J-Alves <joao.alves@arm.com>
Change-Id: I75e1d52aab40b3bd699cd486af661804ac2c91d8
diff --git a/src/fdt_patch.c b/src/fdt_patch.c
index d08c1cf..e95b432 100644
--- a/src/fdt_patch.c
+++ b/src/fdt_patch.c
@@ -168,7 +168,7 @@
 	size_t mem_size = pa_difference(mem_begin, mem_end);
 	struct fdt_header *fdt;
 	int fdt_memory_node;
-	int root_offset;
+	int root;
 
 	/* Map the fdt in r/w mode in preparation for updating it. */
 	fdt = mm_identity_map(stage1_locked, fdt_addr,
@@ -193,14 +193,14 @@
 		goto out_unmap_fdt;
 	}
 
-	root_offset = fdt_path_offset(fdt, "/");
+	root = fdt_path_offset(fdt, "/");
 	if (ret < 0) {
 		dlog_error("FDT cannot find root offset. Error: %d\n", ret);
 		goto out_unmap_fdt;
 	}
 
 	/* Add a node to hold the memory information. */
-	fdt_memory_node = fdt_add_subnode(fdt, root_offset, "memory");
+	fdt_memory_node = fdt_add_subnode(fdt, root, "memory");
 	if (fdt_memory_node < 0) {
 		ret = fdt_memory_node;
 		dlog_error("FDT cannot add memory node. Error: %d\n", ret);
@@ -208,7 +208,7 @@
 	}
 
 	/* Set the values for the VM's memory in the FDT. */
-	ret = fdt_appendprop_addrrange(fdt, root_offset, fdt_memory_node, "reg",
+	ret = fdt_appendprop_addrrange(fdt, root, fdt_memory_node, "reg",
 				       mem_start_addr, mem_size);
 	if (ret != 0) {
 		dlog_error(