spl: Only support bl_len when we have to

Aligning addresses and sizes causes overhead which is unnecessary when we
are not loading from block devices. Remove bl_len when it is not needed.

For example, on iot2050 we save 144 bytes with this patch (once the rest of
this series is applied):

add/remove: 0/0 grow/shrink: 0/3 up/down: 0/-144 (-144)
Function                                     old     new   delta
spl_load_simple_fit                          920     904     -16
load_simple_fit                              496     444     -52
spl_spi_load_image                           384     308     -76
Total: Before=87431, After=87287, chg -0.16%

We use panic() instead of BUILD_BUG_ON in spl_set_bl_len because we still
need to be able to compile it for things like mmc_load_image_raw_sector,
even if that function will not be used.

Signed-off-by: Sean Anderson <seanga2@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/common/spl/spl_nor.c b/common/spl/spl_nor.c
index 236b071..aad230d 100644
--- a/common/spl/spl_nor.c
+++ b/common/spl/spl_nor.c
@@ -49,7 +49,7 @@
 			int ret;
 
 			debug("Found FIT\n");
-			load.bl_len = 1;
+			spl_set_bl_len(&load, 1);
 			load.read = spl_nor_load_read;
 
 			ret = spl_load_simple_fit(spl_image, &load,
@@ -97,7 +97,7 @@
 #ifdef CONFIG_SPL_LOAD_FIT
 	if (image_get_magic(header) == FDT_MAGIC) {
 		debug("Found FIT format U-Boot\n");
-		load.bl_len = 1;
+		spl_set_bl_len(&load, 1);
 		load.read = spl_nor_load_read;
 		return spl_load_simple_fit(spl_image, &load,
 					   spl_nor_get_uboot_base(),
@@ -106,7 +106,7 @@
 #endif
 	if (IS_ENABLED(CONFIG_SPL_LOAD_IMX_CONTAINER) &&
 	    valid_container_hdr((void *)header)) {
-		load.bl_len = 1;
+		spl_set_bl_len(&load, 1);
 		load.read = spl_nor_load_read;
 		return spl_load_imx_container(spl_image, &load,
 					      spl_nor_get_uboot_base());
@@ -114,7 +114,7 @@
 
 	/* Legacy image handling */
 	if (IS_ENABLED(CONFIG_SPL_LEGACY_IMAGE_FORMAT)) {
-		load.bl_len = 1;
+		spl_set_bl_len(&load, 1);
 		load.read = spl_nor_load_read;
 		return spl_load_legacy_img(spl_image, bootdev, &load,
 					   spl_nor_get_uboot_base(),