Staging: hv: mousevsc: Properly add the hid device

We need to properly add the hid device to correctly initialize the
sysfs state. While this patch is against the staging tree; Jiri,
please pick up this patch as you merge the Hyper-V mouse driver.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Reported-by: Fuzhou Chen <fuzhouch@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>