[MIPS] Namespace clean-up in arch/mips/pci/pci.c

The following symbols

	hose_head
	hose_tail

are needlessly defined global in arch/mips/pci/pci.c, and
this patch makes them static.

The variable pci_isa_hose is not used, and is removed by
this patch.

Spotted by namespacecheck. Tested by booting a Malta 4Kc
board up to the shell prompt.

Signed-off-by: Dmitri Vorobiev <dmitri.vorobiev@movial.fi>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>