boot/bootutil: Fix probable uninitialized flash_area access

The commit fixes issue where failed flash_area_open in
boot_write_status would result in flash_area_close call on
uninitialized flash_area object.

Signed-off-by: Dominik Ermel <dominik.ermel@nordicsemi.no>
diff --git a/boot/bootutil/src/loader.c b/boot/bootutil/src/loader.c
index e5587dd..b1a4589 100644
--- a/boot/bootutil/src/loader.c
+++ b/boot/bootutil/src/loader.c
@@ -427,7 +427,7 @@
     const struct flash_area *fap;
     uint32_t off;
     int area_id;
-    int rc;
+    int rc = 0;
     uint8_t buf[BOOT_MAX_ALIGN];
     uint8_t align;
     uint8_t erased_val;
@@ -452,8 +452,7 @@
 
     rc = flash_area_open(area_id, &fap);
     if (rc != 0) {
-        rc = BOOT_EFLASH;
-        goto done;
+        return BOOT_EFLASH;
     }
 
     off = boot_status_off(fap) +
@@ -466,13 +465,10 @@
     rc = flash_area_write(fap, off, buf, align);
     if (rc != 0) {
         rc = BOOT_EFLASH;
-        goto done;
     }
 
-    rc = 0;
-
-done:
     flash_area_close(fap);
+
     return rc;
 }
 #endif /* !MCUBOOT_RAM_LOAD */