thunderbolt: Move constants related to NVM into nvm.c

Move constants related to NVM into nvm.c to make the code cleaner. Use a
separate constant for USB4_DATA_DWORDS in usb4.c.

No functional changes.

Signed-off-by: Gil Fine <gil.fine@linux.intel.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>