Use list_for_each_entry() helper instead of explicit combo of
list_for_each() and list_entry().

Note that pos is used as a reference point in list_add_tail() in
icom_alloc_adapter(). This functionality remains as with an empty list,
cur_adapter_entry->icom_adapter_entry is still the list head.

This simplifies the code a bit.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20220421085808.24152-9-jslaby@suse.czSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>