rs: Fix build with ISO C++ 11 compilers

ISO C++ 11 no longer allows implicit narrowing during initialization

Change-Id: Iec3726fc12379e17300a372619378b77d033d841
Signed-off-by: Bernhard Rosenkraenzer <Bernhard.Rosenkranzer@linaro.org>
Merge pull request #1 from nocoast/jb2

rs: Fix build with ISO C++ 11 compilers