thunderbolt: Refactor add_switch() into two functions

Currently add_switch() takes a huge amount of parameters that makes it
hard to maintain. Instead of passing all those parameters we can split
the function into two parts (alloc and add) and fill the additional
switch fields directly in the functions calling those.

While there remove redundant error logging in case kmemdup() fails.

No functional changes.

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