Staging: hv: mousevsc: Handle the case where we may get bogus report desc size

Handle the case where we may get bogus report desc size from the host.

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