usb: dwc3: Don't include asm-generic/io.h

This can conflict with asm/io.h on some archs, and it isn't needed to build
dwc3-generic.c
Signed-off-by: NSean Anderson <seanga2@gmail.com>
Tested-by: NPatrick Delaunay <patrick.delaunay@st.com>

drivers/usb/dwc3/dwc3-generic.c

@@ -10,7 +10,6 @@
 #include <common.h>
 #include <cpu_func.h>
 #include <log.h>
-#include <asm-generic/io.h>
 #include <dm.h>
 #include <dm/device-internal.h>
 #include <dm/lists.h>