ARM: tegra: remove warnings timer.c and cpu_timer_arch.c

ARM: tegra: remove warnings timer.c and cpu_timer_arch.c

remove readl and writel from cpu_timer_arch (not used)

readl and writel code is in timer.h -- use it
remove unused variable

Change-Id: I2286b66c356ebb7970d00921c852f63a0d014528
Signed-off-by: Philip Rakity <prakity@nvidia.com>
Reviewed-on: http://git-master/r/270782
Reviewed-by: Diwakar Tundlam <dtundlam@nvidia.com>
Reviewed-by: Laxman Dewangan <ldewangan@nvidia.com>
(cherry picked from commit 374c02ad51a822c7997e03b3b6c640ea660b4b65)
Signed-off-by: Ajay Nandakumar <anandakumarm@nvidia.com>