dtoc: Add a 64-bit type and a way to convert cells into 64 bits

When dealing with multi-cell values we need a type that can hold this
value. Add this and a function to process it from a list of cell values.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Tested-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Tested-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/tools/dtoc/fdt.py b/tools/dtoc/fdt.py
index 49409a6..ffd42ce 100644
--- a/tools/dtoc/fdt.py
+++ b/tools/dtoc/fdt.py
@@ -21,7 +21,7 @@
 # so it is fairly efficient.
 
 # A list of types we support
-(TYPE_BYTE, TYPE_INT, TYPE_STRING, TYPE_BOOL) = range(4)
+(TYPE_BYTE, TYPE_INT, TYPE_STRING, TYPE_BOOL, TYPE_INT64) = range(5)
 
 def CheckErr(errnum, msg):
     if errnum: