modules: mark find_symbol static

commit 773110470e2fa3839523384ae014f8a723c4d178 upstream.

find_symbol is only used in module.c.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jessica Yu <jeyu@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>