nand: spl_loaders: Only read enough pages to load the image

All other implementations of nand_spl_load_image only read as many pages as
are necessary to load the image. However, nand_spl_loaders.c loads the full
block. Align it with other load functions so that it is easier to
determine how large of a load buffer we need.

Signed-off-by: Sean Anderson <seanga2@gmail.com>
Reviewed-by: Michael Trimarchi <michael@amarulasolutions.com>
diff --git a/drivers/mtd/nand/raw/nand_spl_loaders.c b/drivers/mtd/nand/raw/nand_spl_loaders.c
index 35d6b1d..db4213e 100644
--- a/drivers/mtd/nand/raw/nand_spl_loaders.c
+++ b/drivers/mtd/nand/raw/nand_spl_loaders.c
@@ -12,8 +12,11 @@
 	while (block <= lastblock) {
 		if (!nand_is_bad_block(block)) {
 			/* Skip bad blocks */
-			while (page < SYS_NAND_BLOCK_PAGES) {
+			while (size && page < SYS_NAND_BLOCK_PAGES) {
 				nand_read_page(block, page, dst);
+
+				size -= min(size, CONFIG_SYS_NAND_PAGE_SIZE -
+						  page_offset);
 				/*
 				 * When offs is not aligned to page address the
 				 * extra offset is copied to dst as well. Copy