ARM: tegra: remove tegra_chip_uid()

Following commit f5b38c5 "crypto: tegra - use kernel entropy instead
of ad-hoc", this function is no longer used. It's also only accurate
for Tegra20 and not later SoCs. So, remove it.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>