mmc: toshsd: use module_pci_driver to simplify the code

Use the module_pci_driver() macro to make the code simpler
by eliminating module_init and module_exit calls.

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>