uboot-imx

MLK-18376-2 usb: gadget: move utf8_to_utf16le to header file

As other users may use utf8_to_utf16le() to convert the utf8
to utf16 for usb, so move it to head file.

Signed-off-by: Li Jun <jun.li@nxp.com>
(cherry picked from commit 94870cb6b587243e0a68ee9a3ec43540d76152cc)
(cherry picked from commit 80150d76172e4443179ddfe8f91c39126493cffa)