commonlib/fsp.h: include sys/types.h for ssize_t

commonlib/fsp.h: include sys/types.h for ssize_t

This file reportedly didn't compile on SUSE Linux with gcc 4.3.4:

[...]
>     HOSTCC     cbfstool/fsp_relocate.o
> In file included from coreboot/src/commonlib/fsp_relocate.c:18:
> coreboot/src/commonlib/include/commonlib/fsp.h:26: error:
> expected '=', ',', ';', 'asm' or '__attribute__' before
> 'fsp_component_relocate'
[...]

According to POSIX-2008[1], sys/types.h defines ssize_t, so include it.
This should not break coreboot code (as opposed to utils code), as we
have a sys/types.h in src/include.

[1]: http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/sys_types.h.html

Change-Id: Id3694dc76c41d800ba09183e4b039b0719ac3d93
Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Reviewed-on: https://review.coreboot.org/18417
Tested-by: build bot (Jenkins)
Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Martin Roth <martinroth@google.com>