poky.conf: Bump version for 2.6.4 thud release

(From meta-yocto rev: 591984ed1d9f371af0410a91786c60b7cf8e3a5c)

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

meta-poky/conf/distro/poky.conf

@@ -1,6 +1,6 @@
 DISTRO = "poky"
 DISTRO_NAME = "Poky (Yocto Project Reference Distro)"
-DISTRO_VERSION = "2.6.3"
+DISTRO_VERSION = "2.6.4"
 DISTRO_CODENAME = "thud"
 SDK_VENDOR = "-pokysdk"
 SDK_VERSION := "${@'${DISTRO_VERSION}'.replace('snapshot-${DATE}','snapshot')}"