uboot-phytec

disk: introduce get_device()

This patch introduces function get_device(). This looks up a
block_dev_desc_t from an interface name (e.g. mmc) and device number
(e.g. 0). This function is essentially the non-partition-specific
prefix of get_device_and_partition().

Signed-off-by: Stephen Warren <swarren@nvidia.com>