buildroot: Use upstream linux

Signed-off-by: Inochi Amaoto <inochiama@gmail.com>

Author: inochisa

buildroot/configs/naxriscv_sim_raw_defconfig

@@ -55,7 +55,7 @@ BR2_TARGET_ROOTFS_CPIO=y
 
 ## Kernel (litex-rebase branch)
 BR2_LINUX_KERNEL=y
-BR2_LINUX_KERNEL_CUSTOM_GIT=y
+BR2_LINUX_KERNEL_CUSTOM_GIT=n
 BR2_LINUX_KERNEL_CUSTOM_REPO_URL="https://github.com/SpinalHDL/linux.git"
 BR2_LINUX_KERNEL_CUSTOM_REPO_VERSION="dev"
 BR2_LINUX_KERNEL_USE_CUSTOM_CONFIG=y