fs/binfmt_elf.c:load_elf_binary(): return -EINVAL on zero-length mappings

load_elf_binary() returns `retval', not `error'.

Fixes: a87938b2

 ("fs/binfmt_elf.c: fix bug in loading of PIE binaries")
Reported-by: James Hogan <james.hogan@imgtec.com>
Cc: Michael Davidson <md@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>