dfu: flash_img: Removing conditional compilation from header

Applying Coding Guideline rule A.1: Conditional Compilation.

Signed-off-by: Dominik Ermel <dominik.ermel@nordicsemi.no>
diff --git a/include/dfu/flash_img.h b/include/dfu/flash_img.h
index 02e7bde..d71baaa 100644
--- a/include/dfu/flash_img.h
+++ b/include/dfu/flash_img.h
@@ -20,7 +20,6 @@
 	struct stream_flash_ctx stream;
 };
 
-#if defined(CONFIG_IMG_ENABLE_IMAGE_CHECK)
 /**
  * @brief Structure for verify flash region integrity
  *
@@ -31,7 +30,6 @@
 	const uint8_t *match;		/** Match vector data */
 	size_t clen;			/** Content to be compared */
 };
-#endif
 
 /**
  * @brief Initialize context needed for writing the image to the flash.
@@ -81,11 +79,12 @@
 int flash_img_buffered_write(struct flash_img_context *ctx, const uint8_t *data,
 		    size_t len, bool flush);
 
-#if defined(CONFIG_IMG_ENABLE_IMAGE_CHECK)
 /**
  * @brief  Verify flash memory length bytes integrity from a flash area. The
  * start point is indicated by an offset value.
  *
+ * The function is enabled via CONFIG_IMG_ENABLE_IMAGE_CHECK Kconfig options.
+ *
  * @param[in] ctx context.
  * @param[in] fic flash img check data.
  * @param[in] area_id flash area id of partition where the image should be
@@ -96,7 +95,6 @@
 int flash_img_check(struct flash_img_context *ctx,
 		    const struct flash_img_check *fic,
 		    uint8_t area_id);
-#endif
 
 #ifdef __cplusplus
 }