usb: xhci: move ring initialization

usb: xhci: move ring initialization

Move ring initialization from xhci_ring_alloc() to xhci_ring_init().
Call xhci_ring_init() after xhci_ring_alloc(); in the future,
it can also be used to re-initialize the ring during resume.

Additionally, remove xhci_dbg_trace() from xhci_mem_init(). The command
ring's first segment DMA address is now printed during the trace call in
xhci_ring_init().

This refactoring lays also the groundwork for eventually replacing:
* xhci_dbc_ring_init()
* xhci_clear_command_ring()

Signed-off-by: Niklas Neronin <niklas.neronin@linux.intel.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://patch.msgid.link/20260402131342.2628648-9-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>