ALSA: asihpi - Remove useless code in hpi_meter_get_peak()

The hpi_meter_get_peak() function contains the expression
"hm.obj_index = hm.obj_index", which does not carry any semantic load.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 719f82d3

 ("ALSA: Add support of AudioScience ASI boards")
Signed-off-by: Valentina Goncharenko <goncharenko.vp@ispras.ru>
Link: https://lore.kernel.org/r/20220901102814.131855-1-goncharenko.vp@ispras.ru
Signed-off-by: Takashi Iwai <tiwai@suse.de>