ACPI: GTDT: Get rid of acpi_arch_timer_mem_init()

ACPI: GTDT: Get rid of acpi_arch_timer_mem_init()

Since 0f67b56d84b4c ("clocksource/drivers/arm_arch_timer_mmio: Switch
over to standalone driver"), acpi_arch_timer_mem_init() is unused.

Remove it.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Cc: Hanjun Guo <guohanjun@huawei.com>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Cc: Rafael J. Wysocki <rafael@kernel.org>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Mark Rutland <mark.rutland@arm.com>
Acked-by: Hanjun Guo <guohanjun@huawei.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>