selftests/harness: use 1024 in place of LINE_MAX

Android was seeing a compilation error because its C library does not
define LINE_MAX.  Since LINE_MAX is only used to determine the size of
test_name[] and 1024 should be enough for the test name, use 1024 instead
of LINE_MAX.

Link: https://lkml.kernel.org/r/20240509053113.43462-3-tao1.su@linux.intel.com
Fixes: 38c957f0

 ("selftests: kselftest_harness: generate test name once")
Signed-off-by: Tao Su <tao1.su@linux.intel.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Bongsu Jeon <bongsu.jeon@samsung.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Edward Liaw <edliaw@google.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Ivan Orlov <ivan.orlov0322@gmail.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Jarkko Sakkinen <jarkko@kernel.org>
Cc: Jaroslav Kysela <perex@perex.cz>
Cc: Mark Brown <broonie@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Takashi Iwai <tiwai@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>