ARM: 8099/1: EXYNOS: Fix MCPM build with SUSPEND=n

Building of EXYNOS5420_MCPM with disabled SUSPEND fails:
arch/arm/mach-exynos/built-in.o: In function `exynos_mcpm_init':
arch/arm/mach-exynos/mcpm-exynos.c:361: undefined reference to `mcpm_loopback'

The exynos_mcpm_init() in mcp-exynos.c calls mcpm_loopback() which
depends on cpu_suspend function (ARM_CPU_SUSPEND).

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>