linux: re-add CONFIG_MD_LINEAR=m

See: torvalds/linux@127186c

Author: ader1990

sdk_container/src/third_party/coreos-overlay/sys-kernel/coreos-modules/files/commonconfig-6.12

@@ -454,6 +454,7 @@ CONFIG_MAGIC_SYSRQ=y
 CONFIG_MARVELL_PHY=m
 CONFIG_MAX_RAW_DEVS=8192
 CONFIG_MD=y
+CONFIG_MD_LINEAR=m
 CONFIG_MD_RAID0=m
 CONFIG_MEGARAID_MAILBOX=m
 CONFIG_MEGARAID_MM=m