FROMGIT: xhci: dbc: decouple endpoint allocation from initialization

Decouple allocation of endpoint ring buffer from initialization
of the buffer, and initialization of endpoint context parts from
from the rest of the contexts.

It allows driver to clear up and reinitialize endpoint rings
after disconnect without reallocating everything.

This is a prerequisite for the next patch that prevents the transfer
ring from filling up with cancelled (no-op) TRBs if a debug cable is
reconnected several times without transferring anything.

Cc: stable@vger.kernel.org
Fixes: dfba2174 ("usb: xhci: Add DbC support in xHCI driver")
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20250902105306.877476-2-mathias.nyman@linux.intel.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 220a0ffd
https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git

 usb-next)

Bug: 424097777
Change-Id: Ifdb54f81fafb224630a85e35a0569f3b6b604f29
Signed-off-by: Łukasz Bartosik <ukaszb@google.com>