drm/rcar-du: Add missing alpha plane register definitions

#define APnMR_BM_AD		(2 << 4)	/* Auto Display Change Mode */

#define APnMWR			0x0a104

#define APnDSXR			0x0a110

#define APnDSYR			0x0a114

#define APnDPXR			0x0a118

#define APnDPYR			0x0a11c

#define APnDSA0R		0x0a120

#define APnDSA1R		0x0a124

#define APnDSA2R		0x0a128

#define APnSPXR			0x0a130

#define APnSPYR			0x0a134

#define APnWASPR		0x0a138

#define APnWAMWR		0x0a13c

#define APnBTR			0x0a140

#define APnMLR			0x0a150

#define APnSWAPR		0x0a180

/* -----------------------------------------------------------------------------

 * Display Capture Registers