lsi: Properly initialize controller state on reset

The LSI controller was lacking a system reset handler. Simply invoke the
existing soft reset handler in this case. This also allows to drop its
explicit invocation during init.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
