pnp: avoid a small unlikely memory leak in proc_read_escd()

There's a small and unlikely memory leak in
drivers/pnp/pnpbios/proc.c::proc_read_escd().  It's inside a sanity check,
so it probably won't trigger often (if at all), however it *is* a potential
leak and it's easy to avoid, so let's just fix it :)

Signed-off-by: Jesper Juhl <jesper.juhl@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>