platform: msm-shared: Erase the correct block when invalidating ubi fm

When bad blocks are found fastmap needs to be invalidated.
The current code incorrectly invalidates on the 3rd block in the
partition instead of the correct fastmap block.

Fix the code to only invalidate the correct fastmap block.

Change-Id: Ifc854153755c86250d88ac614f6f6be711e8c590
1 file changed