dm: Convert PCI MMC over to use DM PCI API

At present pci_mmc_init() does not correctly use the PCI function since the
list it passes is not terminated. The array size passed to pci_mmc_init() is
actually not used correctly. Fix this and adjust the pci_mmc_init() to scan
all available MMC devices.

Adjust this code to use the new driver model PCI API.

This should move over to the new MMC uclass at some point.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>