configs: stm32mp15: set CONFIG_USB_HUB_DEBOUNCE_TIMEOUT=2s

configs: stm32mp15: set CONFIG_USB_HUB_DEBOUNCE_TIMEOUT=2s

With some USB devices connected on USB HUB for the STMicroelectronics
boards, set the usb_pgood_delay=2 is not enough to ensure a correct
detection for all cases; but it is solved with USB_HUB_DEBOUNCE_TIMEOUT=2s.

For example, issue encountered with the USB flash disk:
    ID 058f:6387 Alcor Micro Corp. Flash Drive

Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>