ipmi: make ipmi_destroy_user() return void

Return value of ipmi_destroy_user() has no meaning, because it's always
zero and callers can do nothing with it. And in most cases it's not
checked. So make this function return void. This also will eliminate static
code analyzer warnings such as unreachable code/redundant comparison when
the return value is checked against non-zero value.

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

Signed-off-by: Vitaliy Shevtsov <v.shevtsov@maxima.ru>
Message-ID: <20241225014532.20091-1-v.shevtsov@maxima.ru>
Signed-off-by: Corey Minyard <corey@minyard.net>