clk: tegra: Do not return 0 on failure

Return values from read_dt_param() will be either TRUE (1) or
FALSE (0), while dfll_fetch_pwm_params() returns 0 on success
or an ERR code on failure.

So this patch fixes the bug of returning 0 on failure.

Fixes: 36541f04 ("clk: tegra: dfll: support PWM regulator control")
Cc: <stable@vger.kernel.org>
Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>