use only zstd for or1k, still some difficulties with ARM nommu

target/linux/config/Config.in.compression

@@ -84,7 +84,8 @@ choice
 prompt "Kernel compression"
 depends on ADK_TARGET_OS_LINUX && !ADK_APPLIANCE_TOOLCHAIN && !ADK_TARGET_CHOOSE_ARCH
 default ADK_LINUX_KERNEL_COMP_GZIP if ADK_TARGET_BOARD_BCM28XX
-default ADK_LINUX_KERNEL_COMP_ZSTD
+default ADK_LINUX_KERNEL_COMP_ZSTD if ADK_TARGET_ARCH_OR1K
+default ADK_LINUX_KERNEL_COMP_XZ
 
 config ADK_LINUX_KERNEL_COMP_ZSTD
 	bool "use Zstandard compression"