binfmt_elf: Fix missing SIGKILL for empty PIE

binfmt_elf: Fix missing SIGKILL for empty PIE

Commit ea08dc5191d9 "fs/binfmt_elf.c: fix bug in loading of PIE
binaries", which was a backport of commit a87938b2e246 upstream,
added a new failure path to load_elf_binary().

Before commit 19d860a140be "handle suicide on late failure exits in
execve() in search_binary_handler()", load_elf_binary() wass
responsible for sending a fatal signal to the task in case of an error
after flushing the old executable.  Add that to the new failure path.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>