spi: pl022: delete description of cur_msg

spi: pl022: delete description of cur_msg

The variable cur_msg was removed, but its description is left behind.
Delete this description.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202312151816.munFeE4L-lkp@intel.com/
Signed-off-by: Nam Cao <namcao@linutronix.de>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://msgid.link/r/f06a9b6eac184cc648ae7444c480add6da87a84d.1702639801.git.namcao@linutronix.de
Signed-off-by: Mark Brown <broonie@kernel.org>