cmd_mmc: default to HW partition 0 if not specified

Currently, "mmc dev 0" does not change the selected HW partition. I
think it makes more sense if "mmc dev 0" is an alias for "mmc dev 0 0",
i.e. that HW partition 0 (main data area) is always selected by default
if the user didn't request a specific partition. Otherwise, the following
happens, which feels wrong:

Select HW partition 1 (boot0):
mmc dev 0 1

Doesn't change the HW partition, so it's still 1 (boot0):
mmc dev 0

With this patch, the second command above re-selects the main data area.

Note that some MMC devices (i.e. SD cards) don't support HW partitions.
However, this patch still works, since mmc_start_init() sets the current
partition number to 0, and mmc_select_hwpart() succeeds if the requested
partition is already selected.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Pantelis Antoniou <panto@antoniou-consulting.com>

common/cmd_mmc.c

@@ -403,7 +403,7 @@ static int do_mmc_part(cmd_tbl_t *cmdtp, int flag,
 static int do_mmc_dev(cmd_tbl_t *cmdtp, int flag,
 		      int argc, char * const argv[])
 {
-	int dev, part = -1, ret;
+	int dev, part = 0, ret;
 	struct mmc *mmc;
 
 	if (argc == 1) {
@@ -426,13 +426,12 @@ static int do_mmc_dev(cmd_tbl_t *cmdtp, int flag,
 	if (!mmc)
 		return CMD_RET_FAILURE;
 
-	if (part != -1) {
 	ret = mmc_select_hwpart(dev, part);
 	printf("switch to partitions #%d, %s\n",
 	       part, (!ret) ? "OK" : "ERROR");
 	if (ret)
 		return 1;
-	}
+
 	curr_device = dev;
 	if (mmc->part_config == MMCPART_NOAVAILABLE)
 		printf("mmc%d is current device\n", curr_device);