P54: use temporary variables to reduce size of generated code

When there are 2 linked structures, using a temporary variable to hold a pointer
to the often used structure usually produces better code (smaller and faster)
since compiler does not have to constantly re-fetch data from the first structure.

Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
Signed-off-by: John W. Linville <linville@tuxdriver.com>