base.bbclass: Expand PNBLACKLIST across multilibs too

base.bbclass: Expand PNBLACKLIST across multilibs too

The PNBLACKLIST feature does not currently work with multilibs,
because they have different ${PN}. The obvious thing to do is to
do this at the same point that we do the PREFERRED_PROVIDER
and PREFERRED_VERSION fixups. (Making the PNBLACKLIST check
do the for-each-multilib check requires it to do the multilib
list generation repeatedly.)

(From OE-Core rev: 9bc0ca9369d0daee94abf60d3d521cc734c7e8cd)

Signed-off-by: Peter Seebach <peter.seebach@windriver.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>