clocksource/drivers/imx-tpm: Add support for ARM64

Allows building and compile-testing the i.MX TPM driver also
for ARM64. The delay_timer is only supported on ARMv7.

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/1585715222-24489-1-git-send-email-Anson.Huang@nxp.com