Add some missing endian conversions in fdt_support.c

Add some missing endian conversions in fdt_support.c

Some functions in fdt_support.c use fdt_getprop to read 32 bit values out of
the device tree, but then use them directly without doing any endian
conversion. Because they check for a value that doesn't actually appear in
practice, the functions continued to work even though they're incorrect.
This change adds the missing conversions.

Signed-off-by: Gabe Black <gabeblack@chromium.org>