thunderbolt: Make tb_switch_find_cap() available to other files

We need to find switch capabilities in order to implement TMU support so
make it available to other files as well.

Signed-off-by: Rajmohan Mani <rajmohan.mani@intel.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Link: https://lore.kernel.org/r/20191217123345.31850-7-mika.westerberg@linux.intel.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>