usbc: explicitly declare sizes of state machines arrays

The asserts in the USB-C stack functions were causing compilation
errors when asserts were enabled in Kconfig.
This was caused because the asserts checked if the functions
parameters were within limits specified by the state machine arrays.
At the position of these asserts, these arrays were only declared
without specifying the size of them, what prohibited the asserts from
knowing the size of arrays and checking if specified value is within
limit of it.

Signed-off-by: Michał Barnaś <mb@semihalf.com>