Add quiet to skiroot kernel command line

Some BMCs have horrifically slow vuarts (or have enough debug options enabled
so that the vuart is horrifically slow), so slow that a 56k modem would
be an upgrade. Due to the amount of early boot messages that Linux outputs,
this can slow down boot a *lot* - in the order of *over* 20 seconds.

Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>
diff --git a/openpower/configs/linux/skiroot_defconfig b/openpower/configs/linux/skiroot_defconfig
index 688524d..4f6c885 100644
--- a/openpower/configs/linux/skiroot_defconfig
+++ b/openpower/configs/linux/skiroot_defconfig
@@ -45,7 +45,7 @@
 CONFIG_PPC_64K_PAGES=y
 CONFIG_SCHED_SMT=y
 CONFIG_CMDLINE_BOOL=y
-CONFIG_CMDLINE="console=tty0 console=hvc0"
+CONFIG_CMDLINE="console=tty0 console=hvc0 quiet"
 # CONFIG_SECCOMP is not set
 CONFIG_PCI_MSI=y
 CONFIG_NET=y