MA-20027 change CONFIG_KFENCE_SAMPLE_INTERVAL to 500

To align the Kfence sample interval value to the GKI one.

TEST: run vts -m KernelApiSysfsTest -t
com.android.tests.sysfs.KernelApiSysfsTest#testKfenceSampleRate

Change-Id: Id6809a1ff215fc8f9ccaa00f83dc0c3443cc3b6d
Signed-off-by: Haoran.Wang <elven.wang@nxp.com>