backends/hostmem: Fix block comments style (checkpatch.pl warnings)

backends/hostmem: Fix block comments style (checkpatch.pl warnings)

While re-indenting code in host_memory_backend_memory_complete(),
we triggered various "Block comments use a leading /* on a separate
line" warnings from checkpatch.pl. Correct the comments style.

Fixes: e199f7ad4d ("backends: Simplify host_memory_backend_memory_complete()")
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>