sparc: kernel/pcic: silence gcc 7.x warning in pcibios_fixup_bus()

When building the kernel for Sparc using gcc 7.x, the build fails
with:

arch/sparc/kernel/pcic.c: In function ‘pcibios_fixup_bus’:
arch/sparc/kernel/pcic.c:647:8: error: ‘cmd’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
    cmd |= PCI_COMMAND_IO;
        ^~

The simplified code looks like this:

unsigned int cmd;
[...]
pcic_read_config(dev->bus, dev->devfn, PCI_COMMAND, 2, &cmd);
[...]
cmd |= PCI_COMMAND_IO;

I.e, the code assumes that pcic_read_config() will always initialize
cmd. But it's not the case. Looking at pcic_read_config(), if
bus->number is != 0 or if the size is not one of 1, 2 or 4, *val will
not be initialized.

As a simple fix, we initialize cmd to zero at the beginning of
pcibios_fixup_bus.
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

arch/sparc/kernel/pcic.c

@@ -602,7 +602,7 @@ void pcibios_fixup_bus(struct pci_bus *bus)
 {
 	struct pci_dev *dev;
 	int i, has_io, has_mem;
-	unsigned int cmd;
+	unsigned int cmd = 0;
 	struct linux_pcic *pcic;
 	/* struct linux_pbm_info* pbm = &pcic->pbm; */
 	int node;