platform/chrome: cros_ec_typec: zero out stale pointers

In the Linux kernel, the following vulnerability has been resolved:

platform/chrome: cros_ec_typec: zero out stale pointers

`cros_typec_get_switch_handles` allocates four pointers when obtaining

type-c switch handles. These pointers are all freed if failing to obtain

any of them; therefore, pointers in `port` become stale. The stale

pointers eventually cause use-after-free or double free in later code

paths. Zeroing out all pointer fields after freeing to eliminate these

stale pointers.