include: drivers: usb_c: unify status register data type to uint32_t

The tcpc_get_status_register function was using int32_t for the status
parameter, while the other related functions used uint32_t. This change
unifies the data type across all related functions to uint32_t for
consistency and clarity.

Signed-off-by: Jianxiong Gu <jianxiong.gu@outlook.com>