usb: xhci: improve TR Dequeue Pointer mask

usb: xhci: improve TR Dequeue Pointer mask

Address the naming and usage of the TR Dequeue Pointer mask in the xhci
driver. The Endpoint Context Field at offset 0x08 is defined as follows:
 Bit 0		Dequeue Cycle State (DCS)
 Bits 3:1	RsvdZ (Reserved and Zero)
 Bits 63:4	TR Dequeue Pointer

When extracting the TR Dequeue Pointer for an Endpoint without Streams,
in xhci_handle_cmd_set_deq(), the inverted Dequeue Cycle State mask
(~EP_CTX_CYCLE_MASK) is used, inadvertently including the Reserved bits.
Although bits 3:1 are typically zero, using the incorrect mask could cause
issues.

The existing mask, named "SCTX_DEQ_MASK," is misleading because "SCTX"
implies exclusivity to Stream Contexts, whereas the TR Dequeue Pointer is
applicable to both Stream and non-Stream Contexts.

Rename the mask to "TR_DEQ_PTR_MASK", utilize GENMASK_ULL() macro and use
the mask when handling the TR Dequeue Pointer field.

Function xhci_get_hw_deq() returns the Endpoint Context Field 0x08, either
directly from the Endpoint context or a Stream.

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/20250917210726.97100-5-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>