gdb: fix call to breakpoint_inserted_here_p in darwin-nat.c

Fixes this issue, introduced by f9582a22dba7 ("[gdb] Fix segfault in
for_each_block, part 1"):

       CXX    darwin-nat.o
     /Users/smarchi/src/binutils-gdb/gdb/darwin-nat.c:1169:7: error: no matching function for call to 'breakpoint_inserted_here_p'
       if (breakpoint_inserted_here_p (inf->aspace, pc))
           ^~~~~~~~~~~~~~~~~~~~~~~~~~

Change-Id: I3bb6be75b650319f0fa1dbdceb379b18531da96c