arm64: Add KRYO{3,4}XX CPU cores to spectre-v2 safe list

The "silver" KRYO3XX and KRYO4XX CPU cores are not affected by Spectre
variant 2. Add them to spectre_v2 safe list to correct the spurious
ARM_SMCCC_ARCH_WORKAROUND_1 warning and vulnerability status reported
under sysfs.

Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Tested-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
[will: tweaked commit message to remove stale mention of "gold" cores]
Signed-off-by: Will Deacon <will@kernel.org>