libfdt: Implement fdt_get_property_namelen() and fdt_getprop_namelen()

[Jon Loeliger]

> As well as fdt_subnode_offset(), libfdt includes an
> fdt_subnode_offset_namelen() function that takes the subnode name to
> look up not as a NUL-terminated string, but as a string with an
> explicit length.  This can be useful when the caller has the name as
> part of a longer string, such as a full path.
> 
> However, we don't have corresponding 'namelen' versions for
> fdt_get_property() and fdt_getprop().  There are less obvious use
> cases for these variants on property names, but there are
> circumstances where they can be useful e.g. looking up property names
> which need to be parsed from a longer string buffer such as user input
> or a configuration file, or looking up an alias in a path with
> IEEE1275 style aliases.
> 
> So, since it's very easy to implement such variants, this patch does
> so.  The original NUL-terminated variants are, of course, implemented
> in terms of the namelen versions.
> 
> Signed-off-by: David Gibson <david at gibson.dropbear.id.au>

Applied.

jdl