drm/ast: Rename AST_IO_DAC_INDEX_READ to AST_IO_VGADRR

Rename AST_IO_DAC_INDEX_READ to AST_IO_VGADRR to align naming
in the driver with documentation. No functional changes.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231017083653.10063-6-tzimmermann@suse.de

drivers/gpu/drm/ast/ast_drv.h

@@ -263,7 +263,7 @@ static inline bool __ast_gen_is_eq(struct ast_device *ast, unsigned long gen)
 #define AST_IO_VGAMR_W			(0x42)
 #define AST_IO_VGAER			(0x43)
 #define AST_IO_VGASRI			(0x44)
-#define AST_IO_DAC_INDEX_READ		(0x47)
+#define AST_IO_VGADRR			(0x47)
 #define AST_IO_DAC_INDEX_WRITE		(0x48)
 #define AST_IO_DAC_DATA		        (0x49)
 #define AST_IO_GR_PORT			(0x4E)