usb: dwc3: debugfs: Dump internal LSP and ep registers

To dump internal LSP and endpoint state debug registers, we must write
to GDBGLSPMUX register. This patch correctly dump LSP and endpoint
states from the debug registers.

If the controller is in device mode, all LSP and endpoint state
registers will be dumped via the debugfs attribute "lsp_dump". In host
mode, the user has to write the LSP number to "lsp_dump" to dump a
specific LSP selection.

Fixes: 80b77634

 ("usb: dwc3: Dump LSP and BMU debug info")
Signed-off-by: Thinh Nguyen <thinhn@synopsys.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>