usb: dwc2: debugfs: add support for complete register dump

Dump all registers to take a complete snapshot of dwc2 state.
Code is inspired by dwc3/debugfs.c
Acked-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Mian Yousaf Kaukab <yousaf.kaukab@intel.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/dwc2/core.h

@@ -615,6 +615,7 @@ struct dwc2_hsotg {
 	enum dwc2_lx_state lx_state;
 
 	struct dentry *debug_root;
+	struct debugfs_regset32 *regset;
 
 	/* DWC OTG HW Release versions */
 #define DWC2_CORE_REV_2_71a	0x4f54271a