spl: Convert spl_mmc_load_image() to use linker list

Add a linker list declaration for this method and remove the explicit
switch() code.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/common/spl/spl_mmc.c b/common/spl/spl_mmc.c
index 899caf4..5e8172e 100644
--- a/common/spl/spl_mmc.c
+++ b/common/spl/spl_mmc.c
@@ -267,7 +267,7 @@
 }
 #endif
 
-int spl_mmc_load_image(struct spl_boot_device *bootdev)
+static int spl_mmc_load_image(struct spl_boot_device *bootdev)
 {
 	struct mmc *mmc = NULL;
 	u32 boot_mode;
@@ -345,3 +345,7 @@
 
 	return err;
 }
+
+SPL_LOAD_IMAGE_METHOD(0, BOOT_DEVICE_MMC1, spl_mmc_load_image);
+SPL_LOAD_IMAGE_METHOD(0, BOOT_DEVICE_MMC2, spl_mmc_load_image);
+SPL_LOAD_IMAGE_METHOD(0, BOOT_DEVICE_MMC2_2, spl_mmc_load_image);