drivers/cpufreq: include <module.h> for modular exynos-cpufreq.c code

This file is built off of a tristate Kconfig option ("ARM_EXYNOS_CPUFREQ")
and also contains modular function calls so it should explicitly include
module.h to avoid compile breakage during pending header shuffles.

Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Kukjin Kim <kgene@kernel.org>
Cc: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Acked-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Cc: linux-pm@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-samsung-soc@vger.kernel.org
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>