staging: fbtft: Fix to avoid precedence issues

Parentheses added to avoid operator precedence issues.
Signed-off-by: Rishiraj Manwatkar <manwatkar@outlook.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/fbtft/fb_hx8340bn.c

@@ -157,7 +157,7 @@ static int set_var(struct fbtft_par *par)
  *   OP0 OP1 CP0 CP1 CP2 CP3 CP4 MP0 MP1 MP2 MP3 MP4 MP5 CGM0 CGM1
  *   ON0 ON1 CN0 CN1 CN2 CN3 CN4 MN0 MN1 MN2 MN3 MN4 MN5 XXXX  GC
  */
-#define CURVE(num, idx)  curves[num * par->gamma.num_values + idx]
+#define CURVE(num, idx)  curves[(num) * par->gamma.num_values + (idx)]
 static int set_gamma(struct fbtft_par *par, u32 *curves)
 {
 	unsigned long mask[] = {