usb: renesas_usbhs: Don't disable the pipe if Control write status stage

This patch fixes an issue that sometimes this controller is not able
to complete the Control write status stage.

This driver should enable DCPCTR.CCPL and PID_BUF to complete the status
stage. However, if this driver detects the ctrl_stage interruption first
before the control write data is received, this driver will clear the
PID_BUF wrongly in the usbhsf_pio_try_pop(). To avoid this issue, this
patch doesn't clear the PID_BUF in the usbhsf_pio_try_pop().
(Since also the privious code doesn't disable the PID_BUF after a control
 transfer was finished, this patch doesn't have any side efforts.)

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>