fix tt_command_write()

fix tt_command_write()

1) unbalanced debugfs_file_get().  Not needed in the first place -
file_operations are accessed only via debugfs_create_file(), so
debugfs wrappers will take care of that itself.

2) kmalloc() for a buffer used only for duration of a function is not
a problem, but for a buffer no longer than 16 bytes?

3) strstr() is for finding substrings; for finding a character there's
strchr().

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: "Rafael J. Wysocki" <rafael@kernel.org>
Link: https://lore.kernel.org/r/20250702212542.GH3406663@ZenIV
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>