avr32: use 4.4.x, serial is broken in 4.9.x

target/linux/Config.in.kernelversion

@@ -19,7 +19,7 @@ default ADK_TARGET_LINUX_KERNEL_VERSION_GIT if ADK_TARGET_ARCH_RISCV64
 default ADK_TARGET_LINUX_KERNEL_VERSION_4_4 if ADK_TARGET_ARCH_CRIS
 default ADK_TARGET_LINUX_KERNEL_VERSION_4_4 if ADK_TARGET_ARCH_H8300
 default ADK_TARGET_LINUX_KERNEL_VERSION_4_4 if ADK_TARGET_ARCH_METAG
-default ADK_TARGET_LINUX_KERNEL_VERSION_4_9 if ADK_TARGET_ARCH_AVR32
+default ADK_TARGET_LINUX_KERNEL_VERSION_4_4 if ADK_TARGET_ARCH_AVR32
 default ADK_TARGET_LINUX_KERNEL_VERSION_4_9 if ADK_TARGET_ARCH_BFIN
 default ADK_TARGET_LINUX_KERNEL_VERSION_4_9 if ADK_TARGET_ARCH_FRV
 default ADK_TARGET_LINUX_KERNEL_VERSION_4_9 if ADK_TARGET_CPU_ARM_ARM11MPCORE