of: Make of_find_property_value_of_size take a length range

In preparation for adding variable-length array reads, change
of_find_property_value_of_size so that it takes an optional
maximum length. If the maximum is passed as 0, the behaviour is
unchanged and it will return a property if it's >= the requested
minimum length. If maximum is non-zero it will only return a
property whose length is min <= l <= max.

Signed-off-by: Richard Fitzgerald <rf@opensource.wolfsonmicro.com>
Signed-off-by: Rob Herring <robh@kernel.org>