[media] radio-miropcm20: fix a compilation warning

drivers/media/radio/radio-miropcm20.c: In function 'sanitize':
drivers/media/radio/radio-miropcm20.c:216:3: warning: comparison is always false due to limited range of data type [-Wtype-limits]
   if (p[i] < 32 || p[i] >= 128) {
   ^

As p is declared as a char array, it is signed. So, it can never
be bigger than 127.
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

drivers/media/radio/radio-miropcm20.c

@@ -213,7 +213,7 @@ static bool sanitize(char *p, int size)
 	bool ret = true;
 
 	for (i = 0; i < size; i++) {
-		if (p[i] < 32 || p[i] >= 128) {
+		if (p[i] < 32) {
 			p[i] = ' ';
 			ret = false;
 		}