dm: core: remove meaningless if conditional

If the variable "ret" is equal to "-ENOENT", it is trapped at [1] and
never reaches [2].  At [3], the condition "ret != -ENOENT" is always
true.

  if (ret == -ENOENT) {                       <------------------ [1]
          continue;
  } else if (ret == -ENODEV) {
          dm_dbg("Device '%s' has no compatible string\n", name);
          break;
  } else if (ret) {                           <------------------ [2]
          dm_warn("Device tree error at offset %d\n", offset);
          if (!result || ret != -ENOENT)      <------------------ [3]
                  result = ret;
          break;
  }

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Acked-by: Simon Glass <sjg@chromium.org>