usb: sample: Add support for composite configuration for HID

The current problem with HID is that we need to "patch" static
descriptor table with the size of report descriptor defined in the
user application.

The proposed solution is to have composite_pre_init() defined with
priority CONFIG_KERNEL_INIT_PRIORITY_DEVICE which should run before
composite_init() defined with priority
CONFIG_APPLICATION_INIT_PRIORITY.

Signed-off-by: Andrei Emeltchenko <andrei.emeltchenko@intel.com>