skiboot: Add pflash fix

The skiboot-5.6.0 tag contains a bug that can cause corruption. This
patch is applied to skiboot master, but has not made it to a tag yet.

Change-Id: I8bacd8d8b6083be68a75c4885550204ef34bf363
Signed-off-by: Joel Stanley <joel@jms.id.au>
diff --git a/common/recipes-bsp/skiboot/skiboot.inc b/common/recipes-bsp/skiboot/skiboot.inc
index a20be18..5e943c1 100644
--- a/common/recipes-bsp/skiboot/skiboot.inc
+++ b/common/recipes-bsp/skiboot/skiboot.inc
@@ -3,6 +3,7 @@
 
 SRC_URI += "git://github.com/open-power/skiboot.git;nobranch=1"
 SRC_URI += "file://0001-external-Use-more-standard-PREFIX-vs-prefix.patch"
+SRC_URI += "file://0002-libflash-libffs-Correctly-update-the-actual-size-of-.patch"
 
 FILESEXTRAPATHS_append := "${THISDIR}/skiboot:"