checkpatch: do not require an empty line before error injection

ALLOW_ERROR_INJECTION macro (just like EXPORT_SYMBOL) can immediately
follow a function it annotates.

Link: https://lkml.kernel.org/r/20231109075147.2779461-1-senozhatsky@chromium.org


Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Acked-by: Joe Perches <joe@perches.com>
Cc: Andy Whitcroft <apw@canonical.com> (maintainer:CHECKPATCH)
Cc: Dwaipayan Ray <dwaipayanray1@gmail.com> (reviewer:CHECKPATCH)
Cc: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>