Fix "finish" for vector types on ARM

Fix "finish" for vector types on ARM

On a big-endian ARM system, "finish" printed the wrong value when
finishing from a function that returned a vector type.  Similarly,
calls to a function also resulted in the wrong value being passed.  I
think both the read- and write-functions here should ignore the
endian-ness.

I tested this using the AdaCore internal test suite; the test case
that caught this is identical to gdb.base/gnu_vector.exp.

Approved-By: Luis Machado <luis.machado@arm.com>