disk: part: align buffer so it can be used with DMA enabled drivers

When using ISO partitions with a DMA enabled block device driver
reading the ISO partition leads to unaligned DMA operations:
  CACHE: Misaligned operation at range [bffb7da8, bffb85a8]

Align the buffer to make sure we pass a buffer which works for
DMA operations.
Signed-off-by: NStefan Agner <stefan.agner@toradex.com>
Reviewed-by: NBin Meng <bmeng.cn@gmail.com>

disk/part_iso.c

@@ -24,7 +24,7 @@
 #undef CHECK_FOR_POWERPC_PLATTFORM
 #define CD_SECTSIZE 2048
 
-static unsigned char tmpbuf[CD_SECTSIZE];
+static unsigned char tmpbuf[CD_SECTSIZE] __aligned(ARCH_DMA_MINALIGN);
 
 unsigned long iso_dread(struct blk_desc *block_dev, lbaint_t start,
                         lbaint_t blkcnt, void *buffer)