usb: typec: altmodes/displayport: add irq_hpd to sysfs

usb: typec: altmodes/displayport: add irq_hpd to sysfs

Add irq_hpd sysfs node to displayport driver. This allows the userspace
to subscribe to irq events similar to how it can subscribe to changes in
hpd.

irq_hpd is read only and returns the number of irq events generated since
driver probe. pending_irq_hpd is added so that a sysfs_emit can be
generated if the HPD high event belonging to the same status message
is delayed until a successful configuration.

Signed-off-by: RD Babiera <rdbabiera@google.com>
Reviewed-by: Badhri Jagan Sridharan <badhri@google.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://lore.kernel.org/r/20250623204947.732915-2-rdbabiera@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>