veristat: small fixed found in -O2 mode

Fix few potentially unitialized variables uses, found while building
veristat.c in release (-O2) mode.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20230331222405.3468634-5-andrii@kernel.org


Signed-off-by: Alexei Starovoitov <ast@kernel.org>