mfd: dln2: Automatically detect and fill endpoint pointers

The usb_find_common_endpoints() finds and fills the endpoints
in accordance with their types. Use it to automatically detect
and fill endpoint pointers.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20220617182338.32402-1-andriy.shevchenko@linux.intel.com