usb: xhci: fix comment for PORT_DEV_REMOVE

According to xHCI specification, PORT_DEV_REMOVE(bit 30) in PORTSC
true means "Device is non-removable".
Reported-by: NJuro Bystricky <jurobystricky@hotmail.com>
Signed-off-by: NLu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: NMathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/xhci.h

@@ -358,7 +358,7 @@ struct xhci_op_regs {
 /* wake on over-current (enable) */
 #define PORT_WKOC_E	(1 << 27)
 /* bits 28:29 reserved */
-/* true: device is removable - for USB 3.0 roothub emulation */
+/* true: device is non-removable - for USB 3.0 roothub emulation */
 #define PORT_DEV_REMOVE	(1 << 30)
 /* Initiate a warm port reset - complete when PORT_WRC is '1' */
 #define PORT_WR		(1 << 31)