config: Add default value for CONFIG_SERIAL_ATTACHED_MBIGEN

ascend inclusion
category: bugfix
Bugzilla: N/A
CVE: N/A

----------------------------------------------------
Signed-off-by: NXu Qiang <xuqiang36@huawei.com>
Reviewed-by: NHanjun Guo <guohanjun@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

arch/arm64/configs/hulk_defconfig

@@ -2877,6 +2877,7 @@ CONFIG_SERIAL_OF_PLATFORM=y
 # CONFIG_SERIAL_AMBA_PL010 is not set
 CONFIG_SERIAL_AMBA_PL011=y
 CONFIG_SERIAL_AMBA_PL011_CONSOLE=y
+CONFIG_SERIAL_ATTACHED_MBIGEN=y
 CONFIG_SERIAL_EARLYCON_ARM_SEMIHOST=y
 # CONFIG_SERIAL_KGDB_NMI is not set
 # CONFIG_SERIAL_MAX3100 is not set