docs: kernel-parameters.txt: document xhci-hcd.quirks parameter

This parameter introduced several years ago in the XHCI host controller
driver was somehow left undocumented. Add a few lines in the kernel
parameters text.
Signed-off-by: NLaurentiu Tudor <laurentiu.tudor@nxp.com>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>

Documentation/admin-guide/kernel-parameters.txt

@@ -4846,3 +4846,8 @@
 	xirc2ps_cs=	[NET,PCMCIA]
 			Format:
 			<irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
+
+	xhci-hcd.quirks		[USB,KNL]
+			A hex value specifying bitmask with supplemental xhci
+			host controller quirks. Meaning of each bit can be
+			consulted in header drivers/usb/host/xhci.h.