D2432 (Patch for Amlogic single core PIC) moved the SMP option out
of AML8726 and into board specific config files since some boards
(e.g. YYHD18) use the aml8726-m3 which only have a single core.

r283057 applied most of D2432, however while it removed SMP from
AML8726, it missed adding the SMP option to the board specific
config files.

Differential Revision: https://reviews.freebsd.org/D2589
Submitted by: John Wehle