selftests/bpf: test_verifier verbose log overflows

Tests:
- 458/p ld_dw: xor semi-random 64-bit imms, test 5
- 501/p scale: scale test 1
- 502/p scale: scale test 2

fail in verbose mode due to bpf_vlog[] overflowing. These tests
generate large verifier logs that exceed the current buffer size,
causing them to fail to load.

Increase the size of the bpf_vlog[] buffer to accommodate larger
logs and prevent false failures during test runs with verbose output.

Signed-off-by: Gregory Bell <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Alexei Starovoitov <[e-mail]>

tools/testing/selftests/bpf/test_verifier.c

···
 	BTF_MEMBER_ENC(71, 13, 128), /* struct prog_test_member __kptr *ptr; */
 };
 
-static char bpf_vlog[UINT_MAX >> 8];
+static char bpf_vlog[UINT_MAX >> 5];
 
 static int load_btf_spec(__u32 *types, int types_len,
 			 const char *strings, int strings_len)