Remove CONFIG_USE_FDPIC.

Remove CONFIG_USE_FDPIC.

We want to avoid code disabled by default, because it ends up less
tested. This patch removes all instances of #ifdef CONFIG_USE_FDPIC,
most of which can be safely kept. For the ones that should be
conditionally executed, we define elf_is_fdpic(). Without this patch,
defining CONFIG_USE_FDPIC would prevent QEMU from building precisely
because elf_is_fdpic is not defined.

Signed-off-by: Christophe Lyon <[email protected]>
Reviewed-by: Peter Maydell <[email protected]>
Message-Id: <20180430080404[email protected]>
Signed-off-by: Laurent Vivier <[email protected]>