fstab.common: Fix mmc sdcard path for 6.x and newer kernel versions am: f988e76cb7 am: 02333b37c3

Original change: https://android-review.googlesource.com/c/device/linaro/dragonboard/+/2868694

Change-Id: Idd287996c0195a910f86016b8e844eb7edd480fd
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>