selftests: x86: test_vsyscall: reorder code to reduce #ifdef blocks

selftests: x86: test_vsyscall: reorder code to reduce #ifdef blocks

There are multiple #ifdef blocks inside functions where they return just
0 if #ifdef is false. This makes number of tests counting difficult.
Move those functions inside one #ifdef block and move all of them
together. This is preparatory patch for next patch to convert this into
TAP format. So in this patch, we are just moving functions around
without any changes.

With and without this patch, the output of this patch is same.

Signed-off-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>