kselftest/arm64: Fix redundancy of a testcase

Currently, we are writing the same value as we read into the TLS
register, hence we cannot confirm update of the register, making the
testcase "verify_tpidr_one" redundant. Fix this.
Signed-off-by: Dev Jain <dev.jain@arm.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20240605115448.640717-1-dev.jain@arm.com
[catalin.marinas@arm.com: remove the increment style change]
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

tools/testing/selftests/arm64/abi/ptrace.c

@@ -47,7 +47,7 @@ static void test_tpidr(pid_t child)
 
 	/* ...write a new value.. */
 	write_iov.iov_len = sizeof(uint64_t);
-	write_val[0] = read_val[0]++;
+	write_val[0] = read_val[0] + 1;
 	ret = ptrace(PTRACE_SETREGSET, child, NT_ARM_TLS, &write_iov);
 	ksft_test_result(ret == 0, "write_tpidr_one\n");