driver/bluetooth/h4_ifx_cyw43xxx: Allow CBUCK regulator to discharge

Problem:
re-plug USB (e.g cy8cproto_062_4343w kit) can cause that
CY43xx device become unresponsive (cy8cproto_062_4343w).
As result we catch ASSERTION FAIL (timeout) on HCI_Reset command.

Fix: added delay (BT_POWER_CBUCK_DISCHARGE_TIME_MS) to be sure
that BT CBUCK regulator to discharge.

Tested on:
cy8cproto_062_4343w, cy8ckit_062s2_ai and cy8ckit_062s2_43012 kits.

Signed-off-by: Nazar Palamar <nazar.palamar@infineon.com>