p0004: make perf test executable

It looks like in 89c3b0a (name-hash: add perf test for lazy_init_name_hash,
2017-03-23) p0004 was not created with the execute unix rights.
Let's fix that.

Signed-off-by: Christian Couder <[email protected]>
Acked-by: Jeff Hostetler <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: chriscool