dbg-log for Spreadtrum platforms

Required properties:
- compatible: should be one of following:
	"sprd,dbg-log-sharkl3",
	"sprd,dbg-log-sharkl5",
	"sprd,dbg-log-roc1",
	"sprd,dbg-log-orca".
- reg: Specify the physical base address of the controller and length
  	of memory mapped region.
- sprd,syscon-mm-ahb:
	use to get phy mm ahb address.
- sprd,syscon-aon-apb:
	use to get aon apb address.
- sprd,syscon-dsi-apb:
	use to get phy dsi apb address.
- sprd,syscon-pll-apb:
	use to get pll address.
- sprd,ch-name:
	channel name list of serdes function supported by hardware.
- sprd,ch-index:
	channel index list of serdes function supported by hardware.
- sprd,dcfix:
	value of dc_blnc_fix(fix DC balance issue of 8b/10b encoder). set to enable.
- sprd,mm:
	call sprd_cam_pw_on function to power mm on. set to enable.
- vddio-supply:
	To let sensor power on for MIPI SWITCH working. this property is optional.
- mipi-switch-en-gpio:
	enable the MIPI SWITCH
- mipi-switch-mode-gpio:
	select the rear camera for MIPI SWITCH

Examples:
	modem_dbg_log: modem-dbg-log@324f0000 {
		compatible = "sprd,dbg-log-sharkl5";
		reg = <0 0x324f0000 0 0x4000>;
		sprd,syscon-mm-ahb = <&mm_ahb_regs>;
		sprd,syscon-dsi-apb = <&anlg_phy_g10_regs>;
		sprd,ch-name = "TRAINING", "WTL", "MDAR", "TPIU", "DBUS", "WCN";
		sprd,ch-index = <15 1 0 2 3 4>;
		sprd,dcfix;
		sprd,mm;
		status = "disabled";
	};

