Same as with the off_t, some syscalls were using
incorrect size parametres in place of a guest-defined
size_t. This commit changes the signature of said
syscalls and adds the size_t typedef to the
arch-dependent Linux OSs.
Change-Id: Iece43814971a8e6275d25f6789e41528d241d1f4
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>