HID: amd_sfh: Allow configuring whether HPD is enabled or disabled

HID: amd_sfh: Allow configuring whether HPD is enabled or disabled

Human presence detection (HPD) sensor uses a camera to determine when
user is physically in front of the machine.  This might not be a
desirable behavior because it can (for example) cause the machine to
wake on approach.

Add a new sysfs file "hpd" that will control whether this sensor is
enabled. Use the value of this sysfs file to turn off HPD and prevent
it from re-enabling after resume from suspend.

Cc: Pratap Nirujogi <pratap.nirujogi@amd.com>
Tested-by: Anson Tsao <anson.tsao@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Jiri Kosina <jkosina@suse.com>