Kconfig: Migrate BOUNCE_BUFFER

The bounce buffer is used by a few drivers (most of the MMC drivers)
to overcome limitations in their respective DMA implementation.

This moves the configuration to Kconfig and makes it user-selectable
(even though it will be a required feature to make those drivers
work): the expected usage is for drivers depending on this to 'select'
it unconditionally from their respective Kconfig (see follow-up
patches).

This commit includes a full migration using moveconfig.py to ensure
that each commit compiles.  To ensure bisectability we update
dependencies of various drivers to now select BOUNCE_BUFFER when needed.

[trini: Squash all patches to ensure bisectability]
Signed-off-by: Tom Rini <trini@konsulko.com>
Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Otavio Salvador <otavio@ossystems.com.br> [dw_mmc portion]
Reviewed-by: Fabio Estevam <festevam@gmail.com> [mxsmmc portion]
Reviewed-by: Simon Glass <sjg@chromium.org> [tegra portion]
diff --git a/configs/nitrogen6dl_defconfig b/configs/nitrogen6dl_defconfig
index 80c9d81..9072c04 100644
--- a/configs/nitrogen6dl_defconfig
+++ b/configs/nitrogen6dl_defconfig
@@ -9,6 +9,7 @@
 CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE=y
 CONFIG_SUPPORT_RAW_INITRD=y
 CONFIG_MISC_INIT_R=y
+CONFIG_BOUNCE_BUFFER=y
 CONFIG_BOARD_EARLY_INIT_F=y
 CONFIG_HUSH_PARSER=y
 CONFIG_CMD_BOOTZ=y