tinyalsa: fix musl build

Add a patch adding missing header to fix build with musl.

Fixes:
http://autobuild.buildroot.net/results/de9/de97fbd0b9c88bb5d9aa81ea6d73cdcaadb9c763/



Cc: Maxime Hadjinlian <maxime.hadjinlian@gmail.com>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>