XER10-2143: [Eco mode]5G and 6G BSSIDs are down after a reboot and FR.

[sowmiyachelliah]

Reason for change: XER10-1174 changes broke Eco mode due to kernel nvram setting
didn't get preserved. From other BRCM wifi projects, rdkb never corrupted
kernel_nvram.setting file and assumed factory process may have intruduce invalid
kernel nvram setting. This changes is to remove /data/.kernel_nvram.setting on first
boot if there is no other known files created by RDKB.

Test Procedure:
Please be careful that you are running latest build or xer10 will end up in boot loop.
1) create corrupted /data/.kernel_nvram.setting; "rm -rf /data/.kernel_nvram.setting; echo "123" > /data/.kernel_nvram.setting; sync; reboot -f"
2) check if xer10 comes up correctly.
3) run "nvram kset Hellow=World; nvram kcommit.
4) Reboot, check "nvram kget Hellow" and it should return "World".
5) perform Factory Default, and run step 4 but make sure nothing return this time

Change-Id: I488d5f20393086f4b040bc873e0bc26de855f3a8 Risks: Low
Signed-off-by: [email protected]
(cherry picked from commit 59531e09eec6b4a40b16f9bfc9a5d5bee613c129)

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