xhci: Clean up stale comment on ERST_SIZE macro

Commit ebd88cf ("xhci: Remove unused defines for ERST_SIZE and
ERST_ENTRIES") removed the ERST_SIZE macro but retained a code comment
explaining the quantity chosen in the macro.

Remove the code comment as well.

Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20231019102924.2797346-11-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: l1k

drivers/usb/host/xhci.h

@@ -1643,12 +1643,7 @@ struct urb_priv {
 	struct	xhci_td	td[];
 };
 
-/*
- * Each segment table entry is 4*32bits long.  1K seems like an ok size:
- * (1K bytes * 8bytes/bit) / (4*32 bits) = 64 segment entries in the table,
- * meaning 64 ring segments.
- * Reasonable limit for number of Event Ring segments (spec allows 32k)
- */
+/* Reasonable limit for number of Event Ring segments (spec allows 32k) */
 #define	ERST_MAX_SEGS	2
 /* Poll every 60 seconds */
 #define	POLL_TIMEOUT	60