arm64: dts: qcom: sc8280xp: add aliases for i2c4 and i2c21

Add aliases for i2c4 and i2c21 to the crd and x13s DTS files so that
what's exposed to userspace doesn't change in the future if additional
i2c buses are enabled on these platforms.

Signed-off-by: Brian Masney <bmasney@redhat.com>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230103182229.37169-10-bmasney@redhat.com