platform: tegra: emc: Move timer function defs

platform: tegra: emc: Move timer function defs

Move the timer function defs to tegra_emc.h from tegra21_emc.h since
these function are visible to all chips even if they don't actually
do anything.

Change-Id: I91bc34ad9b10a0cadd1566d14f7fa866cd97652e
Signed-off-by: Alex Waterman <alexw@nvidia.com>
Reviewed-on: http://git-master/r/747447
Reviewed-by: Sachin Nikam <snikam@nvidia.com>
Reviewed-by: Aleksandr Frid <afrid@nvidia.com>
Reviewed-by: Alankrita G <alankritag@nvidia.com>
Reviewed-by: Yu-Huan Hsu <yhsu@nvidia.com>