[PATCH] USB: g_file_storage: add comment about buffer allocation

This patch (as664) adds a comment to file_storage.c, noting that the
driver is slightly non-portable because it assumes that a buffer
allocated for a bulk-in endpoint will also be useable for a bulk-out
endpoint.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>