ARC: Improve relocation fix-ups

ARC: Improve relocation fix-ups

We used to have the one and only linker script for all ARC boards
and so we relied on a particular order of symbols there.

Because of that we used __ivt_end as the marker of the end of all the
code which won't be true any longer if we move .ivt section to any other
place. That said we'd better check for each section separately.

A couple of other improvements:
 1. There's no point to include the marker of section end in interested
    range because its address is beyond the section, i.e. we should
    compare with "<" but not "<=".

 2. .ivt section for ARCv2 cores is just an array of 32-bit ints and
    they are not swapped even on little-endia cores while in case of
    ARCompact cores .ivt contains valid code so swapping is required.

 3. Just in case add check for ARC600 which is also ARCompact
    and its .ivt is normal code.

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