configure.ac: fix UMP support detection

configure.ac: fix UMP support detection

https://github.com/alsa-project/alsa-utils/commit/b399fb85a919636b7da34e8bcf17f484dd9046f7
added usage of alsa/ump_msg.h without checking whether alsa-lib was
compiled with rawmidi support:
https://github.com/alsa-project/alsa-lib/blob/master/include/Makefile.am#L37

Fixes a build error when alsa-lib was compiled with --disable-rawmidi

aplaymidi.c:34:10: fatal error: alsa/ump_msg.h: No such file or directory
   34 | #include <alsa/ump_msg.h>

Closes: https://github.com/alsa-project/alsa-utils/pull/240
Signed-off-by: Bernd Kuhls <bernd@kuhls.net>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>