selftests: arm64: Clarify output when verifying SVE register set

When verifying setting a Z register via ptrace we check each byte by hand,
iterating over the buffer using a pointer called p and treating each
register value written as a test. This creates output referring to "p[X]"
which is confusing since SVE also has predicate registers Pn. Tweak the
output to avoid confusion here.
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20210913125505.52619-6-broonie@kernel.orgSigned-off-by: Will Deacon <will@kernel.org>

tools/testing/selftests/arm64/fp/sve-ptrace.c

@@ -275,7 +275,7 @@ static int do_parent(pid_t child)
 		if (__BYTE_ORDER == __BIG_ENDIAN)
 			expected = sizeof fpsimd->vregs[0] - 1 - expected;
 
-		ksft_test_result(p[i] == expected, "p[%d] == expected\n", i);
+		ksft_test_result(p[i] == expected, "buf[%d] == expected\n", i);
 		if (p[i] != expected)
 			goto error;
 	}