commit b2d83cfa upstream.

Don't overflow when computing the 64-bit period from 32-bit registers.

Fixes sourceforge bug #2826486.
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>