disk: define nullified functions for !PARTITIONS

Some defconfig enables CMD_PART even if none of any partition table
types (CONFIG_*_PARTITION) are enabled.
This will lead to the size growth in SPL/TPL code since disk/part.c
will be compiled in any way.
We will change disk/Kconfig later so that CONFIG_PARTITIONS is only
enabled when, at least, one of CONFIG_*_PARTITION is enabled.

To make the build work (in particular, "part" command) correctly,
a few functions should be defined as void functions in case of
!CONFIG_PARTITIONS.

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
diff --git a/include/part.h b/include/part.h
index 9975fad..74911f4 100644
--- a/include/part.h
+++ b/include/part.h
@@ -276,6 +276,22 @@
 					  struct disk_partition *info,
 					  int allow_whole_dev)
 { *dev_desc = NULL; return -1; }
+
+static inline int part_get_info_by_name_type(struct blk_desc *dev_desc,
+					     const char *name,
+					     struct disk_partition *info,
+					     int part_type)
+{
+	return -ENOENT;
+}
+
+static inline int part_get_info_by_name(struct blk_desc *dev_desc,
+					const char *name,
+					struct disk_partition *info)
+{
+	return -ENOENT;
+}
+
 static inline int
 part_get_info_by_dev_and_name_or_num(const char *dev_iface,
 				     const char *dev_part_str,