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/bf548-ezkit_defconfig b/configs/bf548-ezkit_defconfig
index 8514d85..19ac4e9 100644
--- a/configs/bf548-ezkit_defconfig
+++ b/configs/bf548-ezkit_defconfig
@@ -1,6 +1,7 @@
 CONFIG_BLACKFIN=y
 CONFIG_TARGET_BF548_EZKIT=y
 CONFIG_BOOTDELAY=5
+CONFIG_SILENT_CONSOLE=y
 CONFIG_CMD_MMC=y
 CONFIG_CMD_SF=y
 CONFIG_CMD_SPI=y