dm: blk: mmc: Tidy up some Makefile rules for SPL

Use the correct SPL_TPL_ variable so that these features can be enabled in
TPL and VPL as needed.

Disable it by default in TPL to avoid any code-size increase. No boards
are actually using it since the Makefile rules don't allow including
drivers/block/ with TPL_DM enabled. It can be manually enabled as needed.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>
diff --git a/drivers/mmc/Makefile b/drivers/mmc/Makefile
index 5d5104b..3a664c2 100644
--- a/drivers/mmc/Makefile
+++ b/drivers/mmc/Makefile
@@ -10,7 +10,7 @@
 obj-$(CONFIG_$(SPL_TPL_)BOOTSTD) += mmc_bootdev.o
 endif
 
-obj-$(CONFIG_$(SPL_)MMC_WRITE) += mmc_write.o
+obj-$(CONFIG_$(SPL_TPL_)MMC_WRITE) += mmc_write.o
 obj-$(CONFIG_MMC_PWRSEQ) += mmc-pwrseq.o
 obj-$(CONFIG_MMC_SDHCI_ADMA_HELPERS) += sdhci-adma.o