When eMMC was formattaed for Linux partition table, "userdata" partition
is missing. In this case, part_get_info_by_name() iterates over all
registered drivers (which are PART_TYPE_EFI, PART_TYPE_DOS and
PART_TYPE_ISO). And when it comes to PART_TYPE_ISO (which has empty
partition table), we can see next warning in U-Boot output:

    ** First descriptor is NOT a primary desc on 1:1 **

This patch switches to part_get_info_by_name_type() API in order to
check only EFI partitions for "userdata" partitions. This eliminates
mentioned warning.

Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
Reviewed-by: Simon Glass <sjg@chromium.org>