spl: mmc: Try to clean up raw-mode options

Make the raw-mode options depend on SPL_SYS_MMCSD_RAW_MODE in a more
direct way. This makes it easier to understand the options with
'make menuconfig'.

There are three different ways of specifying the offset:

- sector offset
- partition number
- partition type

So make these a choice, so it is more obvious what is going on.

Update existing boards to enable SPL_SYS_MMCSD_RAW_MODE where needed.

Reviewed-by: Sean Anderson <seanga2@gmail.com>
Reviewed-by: Quentin Schulz <quentin.schulz@cherry.de>
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/kontron_sl28_defconfig b/configs/kontron_sl28_defconfig
index a1d5f89..c4493e5 100644
--- a/configs/kontron_sl28_defconfig
+++ b/configs/kontron_sl28_defconfig
@@ -51,6 +51,7 @@
 CONFIG_SPL_BOARD_INIT=y
 # CONFIG_SPL_SHARES_INIT_SP_ADDR is not set
 CONFIG_SPL_SYS_MALLOC=y
+CONFIG_SPL_SYS_MMCSD_RAW_MODE=y
 CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_USE_SECTOR=y
 CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR=0x900
 CONFIG_SPL_MPC8XXX_INIT_DDR=y