dfu: Extract common DFU code to handle "dfu_alt_info" environment variable

New dfu_init_env_entities() function has been extracted from cmd_dfu.c and
stored at dfu core.

This is a dfu centric code, so it shall be processed in the core.

Change-Id: I756c5de922fa31399d8804eaadc004ee98844ec2
Signed-off-by: Lukasz Majewski <l.majewski@samsung.com>
Tested-by: Heiko Schocher <hs@denx.de>
diff --git a/include/dfu.h b/include/dfu.h
index 7779710..392cef1 100644
--- a/include/dfu.h
+++ b/include/dfu.h
@@ -113,6 +113,7 @@
 char *dfu_extract_token(char** e, int *n);
 void dfu_trigger_reset(void);
 bool dfu_reset(void);
+int dfu_init_env_entities(char *interface, int dev);
 
 int dfu_read(struct dfu_entity *de, void *buf, int size, int blk_seq_num);
 int dfu_write(struct dfu_entity *de, void *buf, int size, int blk_seq_num);