checkpatch: disable PREFER_SECTION

Zephyr doesn't use the __section macro, so stop warnings like this
from producing a compliance rejection.

WARNING:PREFER_SECTION: __section(.device_) is preferred over
   __attribute__((section(".device_")))
#702: FILE: include/device.h:743:
   __attribute__((__section__(".device_" #level STRINGIFY(prio))))

Signed-off-by: Peter Bigot <peter.bigot@nordicsemi.no>