drm: rockchip: remove depends on ARM_DMA_USE_IOMMU & IOMMU_API

because get recursive dependency problem:
   drivers/video/fbdev/Kconfig:5:error: recursive dependency detected!
   drivers/video/fbdev/Kconfig:5:    symbol FB is selected by DRM_KMS_FB_HELPER
   drivers/gpu/drm/Kconfig:34:    symbol DRM_KMS_FB_HELPER is selected by DRM_ROCKCHIP
   drivers/gpu/drm/rockchip/Kconfig:1:    symbol DRM_ROCKCHIP depends on ARM_DMA_USE_IOMMU
   arch/arm/Kconfig:95:    symbol ARM_DMA_USE_IOMMU is selected by VIDEO_OMAP3
   drivers/media/platform/Kconfig:96:    symbol VIDEO_OMAP3 depends on VIDEO_V4L2
   drivers/media/v4l2-core/Kconfig:6:    symbol VIDEO_V4L2 depends on I2C
   drivers/i2c/Kconfig:7:    symbol I2C is selected by FB_DDC
   drivers/video/fbdev/Kconfig:59:    symbol FB_DDC is selected by FB_CYBER2000_DDC
   drivers/video/fbdev/Kconfig:374:    symbol FB_CYBER2000_DDC depends on FB_CYBER2000
   drivers/video/fbdev/Kconfig:362:    symbol FB_CYBER2000 depends on FB

and ROCKCHIP_IOMMU would select ARM_DMA_USE_IOMMU, so just remove
them.

Signed-off-by: Mark Yao <mark.yao@rock-chips.com>