ALSA: atmel_abdac: clk_round_rate() can return a zero upon error

Treat both negative and zero return values from clk_round_rate()
as errors. This is needed since subsequent patches will convert
clk_round_rate()'s return value to be an unsigned type, rather
than a signed type, since some clock sources can generate rates higher
than (2^31)-1 Hz.

Eventually, when calling clk_round_rate(), only a return value of
zero will be considered a error; all other values will be
considered valid rates. The comparison against values less than
0 is kept to preserve the correct behavior in the meantime.

Signed-off-by: Paul Walmsley <[e-mail]>
Acked-by: Hans-Christian Egtvedt <[e-mail]>
Cc: Nicolas Ferre <[e-mail]>
Signed-off-by: Takashi Iwai <[e-mail]>

sound/atmel/abdac.c

···
 	/* we start at 192 kHz and work our way down to 5112 Hz */
 	while (new_rate >= RATE_MIN && index < (MAX_NUM_RATES + 1)) {
 		new_rate = clk_round_rate(dac->sample_clk, 256 * new_rate);
-		if (new_rate < 0)
+		if (new_rate <= 0)
 			break;
 		/* make sure we are below the ABDAC clock */
 		if (new_rate <= clk_get_rate(dac->pclk)) {