selftests/alsa: Add a few missing gitignore files

selftests/alsa: Add a few missing gitignore files

Compiled binary files should be added to .gitignore

'git status' complains:
Untracked files:
(use "git add <file>..." to include in what will be committed)
     alsa/global-timer
     alsa/utimer-test

Cc: Mark Brown <broonie@kernel.org>
Cc: Jaroslav Kysela <perex@perex.cz>
Cc: Takashi Iwai <tiwai@suse.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>
Link: https://patch.msgid.link/20241122073600.1530791-1-lizhijian@fujitsu.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>