spl: Convert spl_board_load_image() to use linker list

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

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/arch/arm/mach-uniphier/boot-mode/spl_board.c b/arch/arm/mach-uniphier/boot-mode/spl_board.c
index 4eadc2f..e2b202e 100644
--- a/arch/arm/mach-uniphier/boot-mode/spl_board.c
+++ b/arch/arm/mach-uniphier/boot-mode/spl_board.c
@@ -65,7 +65,7 @@
 	return 0;
 }
 
-int spl_board_load_image(struct spl_boot_device *bootdev)
+static int spl_board_load_image(struct spl_boot_device *bootdev)
 {
 	int (*send_cmd)(u32 cmd, u32 arg);
 	int (*card_blockaddr)(u32 rca);
@@ -126,3 +126,4 @@
 
 	return 0;
 }
+SPL_LOAD_IMAGE_METHOD(0, BOOT_DEVICE_BOARD, spl_board_load_image);