usb: dwc2: Changes in registers backup/restore functions

Move hptxfsiz to host register's backup/restore functions, not
needed to have it in global register's backup/restore functions.

Add backup for glpmcfg, and read/write for gi2cctl and pcgcctl.
As requires programming guide.

Affected functions:
dwc2_backup_host_registers()
dwc2_restore_host_registers()
dwc2_backup_global_registers()
dwc2_restore_global_registers()

Signed-off-by: Vardan Mikayelyan <mvardan@synopsys.com>
Signed-off-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Grigor Tovmasyan <tovmasya@synopsys.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>