smbus: Change init priority from DEVICE to DEFAULT

Change init priority for SMBus from KERNEL_INIT_PRIORITY_DEVICE (50)
to KERNEL_INIT_PRIORITY_DEFAULT (40) since other devices which depend
on SMBus (like EEPROM) have the same priority.

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