PM / devfreq: use inclusion <mach/map.h> instead of <plat/map-s5p.h>

This fixes follwoing warning:
In file included from drivers/devfreq/exynos/exynos4_bus.h:15:0,
                 from drivers/devfreq/exynos/exynos4_bus.c:35:
arch/arm/mach-exynos/include/mach/map.h:22:0: warning: "S3C_UART_OFFSET" redefined [enabled by default]
In file included from drivers/devfreq/exynos/exynos4_bus.c:33:0:
arch/arm/plat-samsung/include/plat/map-s5p.h:57:0: note: this is the location of the previous definition

Acked-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>