ARM: arch_timer: add support to configure and enable event stream

ARM: arch_timer: add support to configure and enable event stream

This patch adds support for configuring the event stream frequency
and enabling it.

It also adds the hwcaps definitions to the user to detect this event
stream feature.

Cc: Russell King <linux@arm.linux.org.uk>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Acked-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Sudeep KarkadaNagesha <sudeep.karkadanagesha@arm.com>
(cherry picked from commit e9faebc66ec74f1ab7f267d683b45e80faa69763)
Signed-off-by: Alex Shi <alex.shi@linaro.org>
Conflicts:
	arch/arm/include/asm/arch_timer.h
	arch/arm/include/uapi/asm/hwcap.h
	arch/arm/kernel/setup.c