kconfig: tests: fix recursive inclusion unit test

kconfig: tests: fix recursive inclusion unit test

Adding SPDX license identifier is pretty safe; however, here is one
exception.

Since commit ec8f24b7faaf ("treewide: Add SPDX license identifier -
Makefile/Kconfig"), "make testconfig" would not pass.

When Kconfig detects a circular file inclusion, it displays error
messages with a file name and a line number prefixed to each line.

The unit test checks if Kconfig emits the error messages correctly
(this also checks the line number correctness).

Now that the test input has the SPDX license identifier at the very top,
the line numbers in the expected stderr should be incremented by 1.

Fixes: ec8f24b7faaf ("treewide: Add SPDX license identifier - Makefile/Kconfig")
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>