arm-trusted-firmware-mediatek: skip bad blocks on SPI-NAND (SNFI)

Add patch to skip bad blocks when reading from SPI-NAND. This is needed
in case erase block(s) early in the flash inside the FIP area are bad
and hence need to be skipped in order to be able to boot on such damaged
chips.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>

package/boot/arm-trusted-firmware-mediatek/patches/120-mt7622-bl2_boot_snand-skip-bad-blocks.patch

@@ -0,0 +1,40 @@
+--- a/plat/mediatek/mt7622/bl2_boot_snand.c
++++ b/plat/mediatek/mt7622/bl2_boot_snand.c
+@@ -21,6 +21,10 @@
+ #define FIP_BASE			0x80000
+ #define FIP_SIZE			0x200000
+
++#ifndef NMBM
++#define SNAND_MAX_BAD_BLOCK		3
++#endif
++
+ struct snfi_gpio_mux_info {
+ 	const uint32_t *pins;
+ 	uint32_t count;
+@@ -45,12 +49,26 @@ static size_t snand_read_range(int lba,
+ 	size_t sizeremain = size, chunksize;
+ 	uint64_t off = lba * cinfo.pagesize;
+ 	uint8_t *ptr = (uint8_t *)buf;
++	struct mtk_snand_chip_info info;
++	unsigned int bad_blocks = 0;
+ 	int ret = 0;
+
+ 	if (!snf)
+ 		return 0;
+
++	ret = mtk_snand_get_chip_info(snf, &info);
++	if (ret)
++		return 0;
++
+ 	while (sizeremain) {
++		while (mtk_snand_block_isbad(snf, off)) {
++			if (bad_blocks > SNAND_MAX_BAD_BLOCK)
++				return size - sizeremain;
++
++			off += info.blocksize;
++			++bad_blocks;
++		}
++
+ 		chunksize = cinfo.pagesize;
+ 		if (chunksize > sizeremain)
+ 			chunksize = sizeremain;