package.bbclass: Use expanded RDEPENDS in read_shlibdeps

package.bbclass: Use expanded RDEPENDS in read_shlibdeps

We may as well expand the RDEPENDS when reading and writing as this function does.
if we don't do this, we could accidentally duplicate data and it also turns out
to be much less efficient.

(From OE-Core rev: d62a3151e7b252911c172a605b3089de355663c5)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>