We don't care much about I$ line length really as there're
no per-line ops on I$ instead we only do full invalidation of it
on occasion of relocation and right before jumping to the OS.

Also as compared to Linux kernel where we don't support different
lengths of I$ and D$ lines in U-Boot we have to deal with such an
exotic configs if the target board is not supposed to run Linux kernel.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>