modem-8660: Don't restart non-modem processors in debug mode

Future versions of subsystem_restart() will require calling
subsystem_restart() with a pointer returned from
subsystem_register(). Remove this call for lpass from the modem
driver so that we can ease the transition.

Change-Id: Ib81016fcc221789ae6b886eb60733ea7273c698e
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>