mmc-erase: Changing the erase functionality

Reverting back to the old erase code of writing 0 to the first block
of the partition, as CMD 35, CMD 36 CMD 38 round down the start
address of the block to be erased to a 2MB aligned address which in
turn erases other partitions erroneously.

Change-Id: I4a239bc73269a8cf1cb128c82947db33a970a6bc
CRs-Fixed: 326149
1 file changed