meta-openpower: fix pflash running

With the latest changes in poky `libflash.so` is not installed in the
rootfs. It causes the error like this:
```
pflash: error while loading shared libraries: libflash.so: cannot open
shared object file: No such file or directory
```

This commit restore the missing symlink.

Tested: `libflash.so` present in the `/usr/lib` and `pflash` works fine.

(From meta-openpower rev: 66c74979d5992f466f243e4b1505d93a4d961744)

Change-Id: I84d015bd145ad0d30cd84d1b76f9cb02262438e2
Signed-off-by: Alexander Filippov <a.filippov@yadro.com>
Signed-off-by: Andrew Geissler <geissonator@yahoo.com>
diff --git a/meta-openpower/recipes-bsp/skiboot/skiboot.inc b/meta-openpower/recipes-bsp/skiboot/skiboot.inc
index e7fbf4a..7140c64 100644
--- a/meta-openpower/recipes-bsp/skiboot/skiboot.inc
+++ b/meta-openpower/recipes-bsp/skiboot/skiboot.inc
@@ -25,3 +25,8 @@
 do_install() {
     oe_runmake -C ${SKIBOOT_SUBDIR} install DESTDIR=${D} prefix=/usr PREFIX=$prefix
 }
+
+# libflash.so is a SONAME and is strongly required in the production
+INSANE_SKIP_${PN}_append = "dev-so"
+FILES_SOLIBSDEV = ""
+FILES_${PN}_append = " ${libdir}/libflash.so"