cnss2: Support enable 32k sleep clk from cnss2

Add one new device tree config item "qcom,sleep-clk-supported"
to support enable 32k internal sleep clock in case it has no
external 32k clk attached in wlan chipset HW. Like qca6390
on some auto platform, host need explicitly tell firmware
to use internal sleep clock, otherwise it will cause LMAC
ps failure.

Change-Id: I52f5d332a912235596eb127ab8e4660355988038
CRs-Fixed: 3448595

cnss2/pci.c

@@ -6762,6 +6762,8 @@ static int cnss_pci_probe(struct pci_dev *pci_dev,
 		goto reset_ctx;
 	}
 
+	cnss_get_sleep_clk_supported(plat_priv);
+
 	ret = cnss_dev_specific_power_on(plat_priv);
 	if (ret < 0)
 		goto reset_ctx;