[BZ #17354] tile: Fix up corner cases with signed relocations

Some types of relocations technically need to be signed rather than
unsigned: in particular ones that are used with moveli or movei,
or for jump and branch.  This is almost never a problem.  Jump and
branch opcodes are pretty much uniformly resolved by the static linker
(unless you omit -fpic for a shared library, which is not recommended).
The moveli and movei opcodes that need to be sign-extended generally
are for positive displacements, like the construction of the address of
main() from _start().  However, tst-pie1 ends up with main below _start
(in a different module) and the test failed due to signedness issues in
relocation handling.

This commit treats the value as signed when shifting (to preserve the
high bit) and also sign-extends the value generated from the updated
bundle when comparing with the desired bundle, which we do to make sure
no overflow occurred.  As a result, the tst-pie1 test now passes.