meta-oe: use BPN in SRC_URI

Fixed SRC_URI:
* ${PN} -> ${BPN}, use ${BP} if it was ${PN}-${PV}
* ${P} -> ${BP}

Otherwise we would meet do_fetch errors when we do the multilib, native
or nativesdk build.

Signed-off-by: Robert Yang <liezhi.yang@windriver.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>

meta-oe/recipes-extended/gnuplot/gnuplot_4.6.5.bb

@@ -1,6 +1,6 @@
 require gnuplot.inc
 
-SRC_URI = "${SOURCEFORGE_MIRROR}/gnuplot/${PN}-${PV}.tar.gz;name=archive \
+SRC_URI = "${SOURCEFORGE_MIRROR}/gnuplot/${BP}.tar.gz;name=archive \
     http://www.mneuroth.de/privat/zaurus/qtplot-0.2.tar.gz;name=qtplot \
     file://subdirs.patch \
     file://lua-loadlibs-configure-in-fix.patch \