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
diff --git a/app/aboot/aboot.c b/app/aboot/aboot.c
index 9f796c0..19d51a8 100644
--- a/app/aboot/aboot.c
+++ b/app/aboot/aboot.c
@@ -842,19 +842,20 @@
 void cmd_erase_mmc(const char *arg, void *data, unsigned sz)
 {
 	unsigned long long ptn = 0;
+	unsigned int out[512] = {0};
 	int index = INVALID_PTN;
-	unsigned long long size;
 
 	index = partition_get_index(arg);
 	ptn = partition_get_offset(index);
-	size = partition_get_size(index);
 
 	if(ptn == 0) {
 		fastboot_fail("Partition table doesn't exist\n");
 		return;
 	}
-	if (mmc_erase_card(ptn, size)) {
-		fastboot_fail("Failed to erase partition\n");
+	/* Simple inefficient version of erase. Just writing
+       0 in first block */
+	if (mmc_write(ptn , 512, (unsigned int *)out)) {
+		fastboot_fail("failed to erase partition");
 		return;
 	}
 	fastboot_okay("");