pinctrl: aspeed: Fix minor documentation error

Kernel test robot throws below warning ->

drivers/pinctrl/aspeed/pinctrl-aspeed-g5.c:2705: warning: This comment
starts with '/**', but isn't a kernel-doc comment. Refer
Documentation/doc-guide/kernel-doc.rst
drivers/pinctrl/aspeed/pinctrl-aspeed-g6.c:2614: warning: This comment
starts with '/**', but isn't a kernel-doc comment. Refer
Documentation/doc-guide/kernel-doc.rst
drivers/pinctrl/aspeed/pinctrl-aspeed.c:111: warning: This comment
starts with '/**', but isn't a kernel-doc comment. Refer
Documentation/doc-guide/kernel-doc.rst
drivers/pinctrl/aspeed/pinmux-aspeed.c:24: warning: This comment starts
with '/**', but isn't a kernel-doc comment. Refer
Documentation/doc-guide/kernel-doc.rst

Fix minor documentation error.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Andrew Jeffery <andrew@aj.id.au>
Link: https://lore.kernel.org/r/1619353584-8196-1-git-send-email-jrdr.linux@gmail.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>