usb: xhci: Set number of event segments and entries to 1

The Linux kernel driver sets the number of event segments and entries
to 1 , while the initial import of the xhci code set that values to 3
for reasons unknown. While most controllers are fine with more event
segments with more entries, there are standard-conformant controllers
(ie. Renesas RCar xHCI) which only support 1 event segment.

Set the number of event segments and event entries back to 1 to allow
such controllers to work with U-Boot xHCI stack. Note that the Renesas
controller correctly indicates ERST Max = 1 in HCSPARAMS2[7:4] .

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Bin Meng <bmeng.cn@gmail.com>