volume: remove duplicated condition.

libavfilter/af_volume.c

@@ -48,9 +48,7 @@ static av_cold int init(AVFilterContext *ctx, const char *args, void *opaque)
         if (*tail) {
             if (!strcmp(tail, "dB")) {
                 /* consider the argument an adjustement in decibels */
-                if (!strcmp(tail, "dB")) {
-                    d = pow(10,d/20);
-                }
+                d = pow(10, d/20);
             } else {
                 /* parse the argument as an expression */
                 ret = av_expr_parse_and_eval(&d, args, NULL, NULL,