tests: disable kernel.sched.preempt and kernel.poll on nrf52810_pca10040

on platform nrf52810_pca10040, the remaining sram space is not enough
to build test cases kernel.sched.preempt and kernel.poll, temporary
exclude nrf52810_pca10040 on that two cases, will open them when issue
is fixed.

Signed-off-by: Wentong Wu <wentong.wu@intel.com>