hv: Add Kconfig menu entry

Most of the drivers/*/Kconfig files define a menu entry. Define
a menu item for hv too such that it becomes uniform with e.g.
virtio for at least "make xconfig" and "make menuconfig" users.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Cc: James Bottomley <JBottomley@Parallels.com>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>