configs/imx6ulpico: Bump to kernel 4.8

Now that the final kernel 4.8 has been released, let's use it
instead of 4.8-rc5.

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

configs/imx6ulpico_defconfig

@@ -17,7 +17,7 @@ BR2_GLOBAL_PATCH_DIR="board/technexion/imx6ulpico/patches"
 # kernel
 BR2_LINUX_KERNEL=y
 BR2_LINUX_KERNEL_CUSTOM_VERSION=y
-BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="4.8-rc5"
+BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="4.8"
 BR2_LINUX_KERNEL_DEFCONFIG="imx_v6_v7"
 BR2_LINUX_KERNEL_CONFIG_FRAGMENT_FILES="board/technexion/imx6ulpico/linux.fragment"
 BR2_LINUX_KERNEL_DTS_SUPPORT=y