Some more issues found by Coverity scanner.

lto-cgraph.c: The code seems to be unused, besides, it's a zero-trip 
loop as parm_num is set to 0 and then checked non nonzeroness.

lto-opts: The check whether first_p is non NULL is always false: All 
calls have a variable ref as argument - and first_p is unconditionally 
dereferenced.

lto_obj_file_open: One could check additionally check "lo" is NULL, but 
that has then to be directly after the XCNEW as already lto_file_init 
dereferences "lo".

Build and regtested on x86-64-gnu-linux

Tobias