sh: pci: Set pci_cache_line_size on SH7780 via the PCICLS register.

The SH7780 PCIC contains a read-only cache line size register that we can
derive pci_cache_line_size from. So, make sure that the software idea of
the cache line size actually matches the host controller's idea.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>