Fix "-smp disable" for emulator with dirty schedulers

Running "erl -smp disable" on an emulator built with dirty scheduler
support caused problems such as segmentation violations and emulator status
line outputs containing garbage. For example:

    $ erl -smp disable
    Segmentation fault (core dumped)

and:

    $ erl -smp disable
    Erlang/OTP 17 [DEVELOPMENT] [erts-6.2] [source] [64-bit] [ds:10:4297895689:4299948152] [async-threads:280]

This problem also caused the emulator smoke_test_SUITE to hit these same
problems if run in an emulator started with the "-smp disable" option.

Fix this segmentation violation by ensuring that dirty scheduler
information is printed in the status line only when the emulator is
compiled with ERTS_SMP enabled.

With this fix in place, the smoke_test_SUITE now passes when the "-smp
disable" option is used, and the emulator status line prints correctly for
both "-smp enable" and "-smp disable":

    $ erl -smp enable
    Erlang/OTP 17 [DEVELOPMENT] [erts-6.2] [source] [64-bit] [smp:8:8] [ds:8:8:10] [async-threads:10] [kernel-poll:false]

and:

    $ erl -smp disable
    Erlang/OTP 17 [DEVELOPMENT] [erts-6.2] [source] [64-bit] [async-threads:10] [kernel-poll:false]