libfdt: return correct value if #size-cells property is not present

According to the device tree specification, the default value for
was not present.

This patch also makes fdt_address_cells() and fdt_size_cells() conform
to the behaviour documented in libfdt.h. The defaults are only returned
if fdt_getprop() returns -FDT_ERR_NOTFOUND, otherwise the actual error
is returned.

This is based on upstream commit:
aa7254d ("libfdt: return correct value if #size-cells property is not present")
but misses the test case part, as we don't implement them in U-Boot.

Signed-off-by: Matthias Brugger <mbrugger@suse.com>
diff --git a/scripts/dtc/libfdt/libfdt.h b/scripts/dtc/libfdt/libfdt.h
index 66f01fe..5c778b1 100644
--- a/scripts/dtc/libfdt/libfdt.h
+++ b/scripts/dtc/libfdt/libfdt.h
@@ -1109,7 +1109,7 @@
  *
  * returns:
  *	0 <= n < FDT_MAX_NCELLS, on success
- *      2, if the node has no #size-cells property
+ *      1, if the node has no #size-cells property
  *      -FDT_ERR_BADNCELLS, if the node has a badly formatted or invalid
  *		#size-cells property
  *	-FDT_ERR_BADMAGIC,