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/ls1021aqds_nand_defconfig b/configs/ls1021aqds_nand_defconfig
index 3beda1e..a822ff0 100644
--- a/configs/ls1021aqds_nand_defconfig
+++ b/configs/ls1021aqds_nand_defconfig
@@ -16,6 +16,7 @@
 CONFIG_SYS_FSL_DDR3=y
 CONFIG_NAND_BOOT=y
 CONFIG_BOOTDELAY=3
+CONFIG_SILENT_CONSOLE=y
 CONFIG_SPL=y
 CONFIG_SPL_MPC8XXX_INIT_DDR_SUPPORT=y
 CONFIG_HUSH_PARSER=y