manual: Document missing options

The -d and -s options were undocumented. Add an entry in the manual.

Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

Documentation/manual.txt

@@ -674,4 +674,8 @@ The fdtdump program prints a readable version of a flat device tree file.
 
 The syntax of the fdtdump command line is:
 
-    fdtdump <DTB-file-name>
+    fdtdump [options] <DTB-file-name>
+
+Where options are:
+    -d,--debug          Dump debug information while decoding the file
+    -s,--scan           Scan for an embedded fdt in given file