boards: st: nucleo_l496zg: add zephyr_udc0 and hsi48 dt nodes

Add Zephyr UDC (USB Device Class) and clk_hsi48 (hi-speed
internal 48 MHz) devicetree nodes so that the nucleo_l496zg
board works with other USB DC samples and tests.

Update the board yaml description to indicate usb and usb
device roles are supported.

Signed-off-by: Chris Friedt <cfriedt@tenstorrent.com>