fbdev: arkfb: Remove the unused function dac_read_reg()

The function dac_read_reg() is defined in the arkfb.c file, but not
called elsewhere, so delete this unused function.

drivers/video/fbdev/arkfb.c:322:18: warning: unused function 'dac_read_reg'.

Link: https://bugzilla.openanolis.cn/show_bug.cgi?id=2155
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: Helge Deller <deller@gmx.de>

Author: Jiapeng Chong

drivers/video/fbdev/arkfb.c

@@ -318,14 +318,6 @@ struct dac_info
 	void *data;
 };
 
-
-static inline u8 dac_read_reg(struct dac_info *info, u8 reg)
-{
-	u8 code[2] = {reg, 0};
-	info->dac_read_regs(info->data, code, 1);
-	return code[1];
-}
-
 static inline void dac_read_regs(struct dac_info *info, u8 *code, int count)
 {
 	info->dac_read_regs(info->data, code, count);