control.h: Fix ump header file detection

control.h: Fix ump header file detection

Apparently, the control.h is used from apps separately (outside
asoundlib.h). Avoid errors like:

/usr/include/alsa/control.h:417:47: error: ‘snd_ump_endpoint_info_t’ has not been declared
  417 | int snd_ctl_ump_endpoint_info(snd_ctl_t *ctl, snd_ump_endpoint_info_t *info);
      |                                               ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/alsa/control.h:418:44: error: ‘snd_ump_block_info_t’ has not been declared
  418 | int snd_ctl_ump_block_info(snd_ctl_t *ctl, snd_ump_block_info_t *info);
      |                                            ^~~~~~~~~~~~~~~~~~~~

Fixes: https://github.com/alsa-project/alsa-lib/issues/348
Signed-off-by: Jaroslav Kysela <perex@perex.cz>