drm/exynos: Fix address space warnings in exynos_drm_fbdev.c

Silences the following warnings:
drivers/gpu/drm/exynos/exynos_drm_fbdev.c:102:40: warning:
incorrect type in assignment (different address spaces)
drivers/gpu/drm/exynos/exynos_drm_fbdev.c:102:40:
expected void [noderef] <asn:2>*kvaddr
drivers/gpu/drm/exynos/exynos_drm_fbdev.c:102:40:    got void *
drivers/gpu/drm/exynos/exynos_drm_fbdev.c:107:48: warning:
incorrect type in assignment (different address spaces)
drivers/gpu/drm/exynos/exynos_drm_fbdev.c:107:48:
expected void [noderef] <asn:2>*kvaddr
drivers/gpu/drm/exynos/exynos_drm_fbdev.c:107:48:    got void *

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Inki Dae <inki.dae@samsung.com>