LF-6072: ASoC: imx-card: Assign clock rate for PDM format

Previously we only assigned clock rate for 44kHz series sample rate.
But meet issue on i.MX8MM 16KHz case, the calculated mclk_freq is
512KHz, but because root clock divider range limitation, the smallest
mclk rate is 768Hkz, then cause issue. so also assign mclk_freq
for 48kHz series sample rates

Fixes: 3a650ee6 ("LF-5909-2: ASoC: imx-card: fix DSD mclk frequency")
Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
Reviewed-by: Chancel Liu <chancel.liu@nxp.com>
Acked-by: Jason Liu <jason.hui.liu@nxp.com>