usb: typec: ucsi: Add debugfs for ucsi commands

usb: typec: ucsi: Add debugfs for ucsi commands

Add support for UCSI commands through the following debugfs:
  # /sys/kernel/debug/usb/ucsi/$UCSI_DEVICE/command
  # /sys/kernel/debug/usb/ucsi/$UCSI_DEVICE/response

Eg: To execute UCSI GetCapabilities:
  # echo 0x6 > /sys/kernel/debug/usb/ucsi/<ucsi device>/command
Then read the result,
  # cat /sys/kernel/debug/usb/ucsi/<ucsi device>/response
    0x02000320000000020000ff0400000445

UCSI command will be written into the command file and the
response for the command can be viewed under the response file.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Saranya Gopal <saranya.gopal@intel.com>
Co-developed-by: Rajaram Regupathy <rajaram.regupathy@intel.com>
Signed-off-by: Rajaram Regupathy <rajaram.regupathy@intel.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://lore.kernel.org/r/20230807105205.742819-1-saranya.gopal@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>