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>
diff --git a/include/part.h b/include/part.h
index a6d06f3..144df4e 100644
--- a/include/part.h
+++ b/include/part.h
@@ -112,6 +112,8 @@
 void print_part (block_dev_desc_t *dev_desc);
 void  init_part (block_dev_desc_t *dev_desc);
 void dev_print(block_dev_desc_t *dev_desc);
+int get_device(const char *ifname, const char *dev_str,
+	       block_dev_desc_t **dev_desc);
 int get_device_and_partition(const char *ifname, const char *dev_str,
 			     block_dev_desc_t **dev_desc,
 			     disk_partition_t *info);
@@ -131,6 +133,9 @@
 static inline void print_part (block_dev_desc_t *dev_desc) {}
 static inline void  init_part (block_dev_desc_t *dev_desc) {}
 static inline void dev_print(block_dev_desc_t *dev_desc) {}
+static inline int get_device(const char *ifname, const char *dev_str,
+	       block_dev_desc_t **dev_desc)
+{ return -1; }
 static inline int get_device_and_partition(const char *ifname,
 					   const char *dev_str,
 					   block_dev_desc_t **dev_desc,