arm: fix up ARM_ARCH_TIMER selects

In 8a4da6e3: "arm: arch_timer: move core to drivers/clocksource", the
selection of ARM_ARCH_TIMER was indirected via HAVE_ARM_ARCH_TIMER,
though mach-exynos's selection of ARM_ARCH_TIMER was missed, and since
then mach-shmobile, mach-tegra, and mach-virt have begun selecting
ARM_ARCH_TIMER. This can lead to architected timer support erroneously
appearing to not be selected in menuconfig.

This patch fixes up the Kconfigs for those platforms to select
HAVE_ARM_ARCH_TIMER.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: Simon Horman <horms+renesas@verge.net.au>
Cc: Kukjin Kim <kgene.kim@samsung.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>