Tegra: fixup CNTPS_TVAL_EL1 delay timer reads

The delay_timer driver for Tegra uses the CNTPS_TVAL_EL1 secure, physical,
decrementing timer as the source. The current logic incorrectly marks this
as an incrementing timer, by negating the timer value.

This patch fixes the anomaly and updates the driver to remove this logic.

Signed-off-by: anzhou <anzhou@nvidia.com>
Change-Id: I60490bdcaf0b66bf4553a6de3f4e4e32109017f4