staging: wilc1000: remove unused string functions

The driver provides wrappers for a lot of string operations.
Some of them are unused, while others should be replaced
with normal kernel functions.

This replaces the unused ones for now, and leaves the other
ones for a later cleanup.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>