karo: tx53: prevent boot failure do to bad blocks inside the U-Boot partition

karo: tx53: prevent boot failure do to bad blocks inside the U-Boot partition

Currently booting from NAND will fail, if the u-boot partition
contains any bad block, since the image_len in the IVT is set to the
u-boot partition size. Apparently the ROM code has a bug and does not
load the last block of a flash image when the block does not end on a
4KiB boundary. This leads to boot failures or random U-Boot crashes,
because the relocation table is most affected by this bug.

Workaround this by padding the image_len stored in the IVT to the next
4KiB boundary.