HID: do not try to compile PM code with CONFIG_PM unset

Fixes this build breakage in case when CONFIG_PM is not set

drivers/hid/usbhid/hid-core.c: In function 'hid_suspend':
drivers/hid/usbhid/hid-core.c:1220: error: 'struct usb_device' has no member named 'auto_pm'
drivers/hid/usbhid/hid-core.c:1245: error: 'struct usb_device' has no member named 'auto_pm'
drivers/hid/usbhid/hid-core.c:1258: error: 'struct usb_device' has no member named 'auto_pm'

by throwing both the hid_suspend() and hid_resume() away completely
in such case, as they won't be used anyway.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>