dfu: samsung: move call to set_dfu_alt_info() to dfu common code

This common call can be used for setting proper entities based
on dfu command arguments.
The config: CONFIG_SET_DFU_ALT_INFO, was used only for few configs,
and now it is common.

The board file should implement:
- set_dfu_alt_info() function

Signed-off-by: Przemyslaw Marczak <p.marczak@samsung.com>
Tested-by: Lukasz Majewski <l.majewski@samsung.com>
[Test HW: Odroid U3 (Exynos 4412)]

include/dfu.h

@@ -140,6 +140,9 @@ struct dfu_entity {
 	unsigned int inited:1;
 };
 
+#ifdef CONFIG_SET_DFU_ALT_INFO
+void set_dfu_alt_info(char *interface, char *devstr);
+#endif
 int dfu_config_entities(char *s, char *interface, char *devstr);
 void dfu_free_entities(void);
 void dfu_show_entities(void);