usb: gadget: configfs: Replace strncpy with strlcpy

Use safer version of strcpy that is strlcpy instead of
strncpy for NULL terminated strings.

Change-Id: I5e2800d1d539545744a1b1231e1d589a7c92797a
Signed-off-by: Manu Gautam <mgautam@codeaurora.org>
Signed-off-by: Chandana Kishori Chiluveru <cchiluve@codeaurora.org>