mm/damon/dbgfs: remove an unnecessary error message

When wrong scheme action is requested via the debugfs interface, DAMON
prints an error message.  Because the function returns error code, this
is not really needed.  Because the code path is triggered by the user
specified input, this can result in kernel log mistakenly being messy.
To avoid the case, this commit removes the message.

Link: https://lkml.kernel.org/r/20211201150440.1088-3-sj@kernel.org


Fixes: af122dd8 ("mm/damon/dbgfs: support DAMON-based Operation Schemes")
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>