Filter: start with enabler "disabled"

Since we can create the enabler, then attach the filter, and then enable
it, ensure it is in a "disabled" state initially.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Remove now unused syscalls.h from lttng-modules

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Migrate ARM, powerpc, MIPS syscall instrumentation to TP_FIELDS

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>