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/popmetal-rk3288_defconfig b/configs/popmetal-rk3288_defconfig
index 2b5b26f..30268e5 100644
--- a/configs/popmetal-rk3288_defconfig
+++ b/configs/popmetal-rk3288_defconfig
@@ -6,6 +6,7 @@
 CONFIG_SPL_STACK_R_ADDR=0x80000
 CONFIG_DEFAULT_DEVICE_TREE="rk3288-popmetal"
 # CONFIG_DISPLAY_CPUINFO is not set
+CONFIG_SILENT_CONSOLE=y
 CONFIG_SPL_STACK_R=y
 CONFIG_SPL_STACK_R_MALLOC_SIMPLE_LEN=0x2000
 CONFIG_HUSH_PARSER=y