kernel: Move to Linux 4.18.3-openpower1

Update to 4.18, and re-generate the defconfig. In addition, make the
following changes:

 - Enable EXPERT, so we can disable some things
 - Disable non-powerpc BPF decoders
 - Disable TASKSTATS
 - Disable unused syscalls
 - Set more things to be modules
 - Turn off unused network vendors

Note that CONFIG_I2C_CHARDEV=y as the module is not loaded
automatically, and without this i2cget etc. will fail.

Buildroot is updated to include support for v4.18.

Signed-off-by: Joel Stanley <joel@jms.id.au>
diff --git a/openpower/linux/0001-xhci-Reset-controller-on-xhci-shutdown.patch b/openpower/linux/0001-xhci-Reset-controller-on-xhci-shutdown.patch
index ee2b1a5..445e666 100644
--- a/openpower/linux/0001-xhci-Reset-controller-on-xhci-shutdown.patch
+++ b/openpower/linux/0001-xhci-Reset-controller-on-xhci-shutdown.patch
@@ -14,10 +14,10 @@
  1 file changed, 1 insertion(+)
 
 diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
-index 5fb4319d7fd1..2c2b55f29563 100644
+index 68e6132aa8b2..ca802b2ba4a7 100644
 --- a/drivers/usb/host/xhci.c
 +++ b/drivers/usb/host/xhci.c
-@@ -717,6 +717,7 @@ static void xhci_shutdown(struct usb_hcd *hcd)
+@@ -781,6 +781,7 @@ static void xhci_shutdown(struct usb_hcd *hcd)
  	/* Yet another workaround for spurious wakeups at shutdown with HSW */
  	if (xhci->quirks & XHCI_SPURIOUS_WAKEUP)
  		pci_set_power_state(to_pci_dev(hcd->self.sysdev), PCI_D3hot);