lib: string: move strlcpy() to a common place

Move strlcpy() definition from drivers/usb/gadget/ether.c to
lib/string.c because it is a very useful function.
Let's add the prototype to include/linux/string.h too.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Acked-by: Simon Glass <sjg@chromium.org>
diff --git a/include/linux/string.h b/include/linux/string.h
index 96348d6..c7047ba 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -30,6 +30,9 @@
 #ifndef __HAVE_ARCH_STRNCPY
 extern char * strncpy(char *,const char *, __kernel_size_t);
 #endif
+#ifndef __HAVE_ARCH_STRLCPY
+size_t strlcpy(char *, const char *, size_t);
+#endif
 #ifndef __HAVE_ARCH_STRCAT
 extern char * strcat(char *, const char *);
 #endif