usb: xhci: move command ring pointer write

usb: xhci: move command ring pointer write

Move command ring pointer write from xhci_mem_init() to xhci_init(),
and utilize the xhci_set_cmd_ring_deq() function.

The xhci_set_cmd_ring_deq() function is nearly identical to the Command
Ring Control register code in xhci_mem_init(). The only notable change is
the use of:
  xhci_trb_virt_to_dma(xhci->cmd_ring->deq_seg, xhci->cmd_ring->dequeue)
instead of:
  xhci->cmd_ring->first_seg->dma
but they are effectively the same in this context. The former represents
the exact position of the dequeue pointer, while the latter is the first
DMA in the first segment. Before use, the dequeue pointer is at the first
DMA in the first segment.

The xhci_set_cmd_ring_deq() function is moved without modification, except
for (long unsigned long) -> (unsigned long long) due to checkpatch.pl.

Signed-off-by: Niklas Neronin <niklas.neronin@linux.intel.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20250515135621.335595-6-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>