staging: mt7621-mmc: Replace sdr_read32 with readl

The current code uses a macro (sdr_read32) for reading from hardware,
but it is only a readl, so replace it to get nearer to upstream code.
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

@@ -948,7 +948,6 @@ struct msdc_host {
 };
 
 #define sdr_read8(reg)            readb(reg)
-#define sdr_read32(reg)           readl(reg)
 #define sdr_write8(reg, val)      writeb(val, reg)
 
 static inline void sdr_set_bits(void __iomem *reg, u32 bs)