staging: mt7621-mmc: Remove unused macro sdr_write8

The macro sdr_write8 is never used, so remove it.
Signed-off-by: Christian Lütke-Stetzkamp <christian@lkamp.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/mt7621-mmc/mt6575_sd.h

@@ -947,8 +947,6 @@ struct msdc_host {
 	u32                         app_cmd_arg;
 };
 
-#define sdr_write8(reg, val)      writeb(val, reg)
-
 static inline void sdr_set_bits(void __iomem *reg, u32 bs)
 {
 	u32 val = readl(reg);