drivers/base: transport_class explicitly requires EXPORT_SYMBOL

This file was getting <linux/module.h> via an implicit include
path, but we want to crush those out of existence since they cost
time during compiles of processing thousands of lines of headers
for no reason.  Give it the lightweight header that just contains
the EXPORT_SYMBOL infrastructure.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>