imx: ocotp: support i.MX6ULL

i.MX6ULL has two 128 bits fuse banks, bank 7 and bank 8,
while other banks use 256 bits. So we have to adjust the
word and bank index when accessing the bank 8.

When in command line `fuse read 8 0 1`, you can image
`fuse read 7 4 1` in the ocotp driver implementation for 6ULL.

When programming, we use word index, so need to fix bank7/8 programming
for i.mx6ull.

For example: fuse prog 8 3 1; The word index is (8 << 3 | 3) --> 67.
But actully it should be (7 << 3 | 7) ---> 63.
So fix it.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Cc: Stefano Babic <sbabic@denx.de>