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/espresso7420_defconfig b/configs/espresso7420_defconfig
index 2281d7e..0ab0437 100644
--- a/configs/espresso7420_defconfig
+++ b/configs/espresso7420_defconfig
@@ -5,6 +5,7 @@
 CONFIG_IDENT_STRING=" for ESPRESSO7420"
 CONFIG_DEFAULT_DEVICE_TREE="exynos7420-espresso7420"
 # CONFIG_DISPLAY_CPUINFO is not set
+CONFIG_SILENT_CONSOLE=y
 CONFIG_SYS_PROMPT="ESPRESSO7420 # "
 # CONFIG_AUTOBOOT is not set
 # CONFIG_CMD_IMLS is not set