usb: host: xhci: fix a comment typo in xhci_mem_init()

It should be Device Context, not doorbell.

Signed-off-by: Linyu Yuan <quic_linyyuan@quicinc.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20220303110903.1662404-7-mathias.nyman@linux.intel.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>