Convert SILENT_CONSOLE options to Kconfig

Move these option to Kconfig and tidy up existing uses.

The Power PC boards don't have a suitable common element: the common header
files don't appear to line up with the Kconfig files as far as I can tell.
This results in a lot of defconfig changes.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Jagan Teki <jteki@openedev.com>
[trini: Re-migrate, update common/console.c logic]
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/cm5200_defconfig b/configs/cm5200_defconfig
index 8b98484..f8e28d9 100644
--- a/configs/cm5200_defconfig
+++ b/configs/cm5200_defconfig
@@ -3,6 +3,7 @@
 CONFIG_TARGET_CM5200=y
 CONFIG_OF_BOARD_SETUP=y
 CONFIG_BOOTDELAY=5
+CONFIG_SILENT_CONSOLE=y
 CONFIG_CMD_ASKENV=y
 CONFIG_LOOPW=y
 CONFIG_CMD_I2C=y