thunderbolt: Move nvm_write_ops to tb.h

Currently these write ops are used for updating router firmware images
only. Moving to tb.h helps the retimers also to use the same ops.

Also add tb_ prefix to the enum while there.

Signed-off-by: Rajmohan Mani <rajmohan.mani@intel.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Change-Id: I5b69eaff3fe2a0e10eb4d29cd30b57ec8a94d9bb