[U-Boot] FAT12 regression after 8d48c92b45aea91e2a2be90f2ed93677e85526f1

Hello,

U-Boot 2017.01 and master branch is broken on BeagleBone Black with boot partition formatted as FAT12, it hang after printing "Loading u-boot.img" message. I bisected regression to this patch:

http://lists.denx.de/pipermail/u-boot/2016-December/276305.html

This code simplification is not going to work on architectures with strict alignment requirements:

+ ret = FAT2CPU16(*(__u16 *)(mydata->fatbuf + off16));

fatbuf is a pointer to __u8 and off16 can take any values so mydata->fatbuf + off16 is not guaranteed to be 16-bits aligned and 16-bit access to non-aligned address will cause exception.