usb: xhci: remove deprecated TODO comment

usb: xhci: remove deprecated TODO comment

The Device Context Base Address Array (DCBAA) contains pointers to device
contexts. These fields are 64-bit registers, capable of holding 64-bit
addresses.

When struct 'xhci_device_context_array' was introduced in commit [1],
the entries were represented as pairs of 'u32', requiring a custom helper
function to set 64-bit addresses. This was later made redundant by
commit [2], which changed the representation to a single 'u64', allowing
direct assignment.

The associated TODO comment referencing the old 32-bit representation is
no longer relevant and is removed.

Link: https://git.kernel.org/torvalds/c/a74588f94655
Link: https://git.kernel.org/torvalds/c/8e595a5d30a5
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/20251119142417.2820519-13-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>