fix GDB build failure for various amd64 targets

The following patch caused some amd64-*-tdep files to fail to compile:

  | commit de52b960
  | Date:   Tue Jun 26 16:33:27 2018 +0100
  | Subject: x86_64-windows GDB crash due to fs_base/gs_base registers

This is because we added one additional "segments" argument to
function amd64_target_description and forgot to update all the callers.
This patch fixes the omissions.

gdb/ChangeLog:

        * amd64-darwin-tdep.c (x86_darwin_init_abi_64): Add missing
        parameter in call to amd64_target_description.
        * amd64-dicos-tdep.c (amd64_dicos_init_abi): Likewise.
        * amd64-fbsd-tdep.c (amd64fbsd_core_read_description)
        (amd64fbsd_init_abi): Likewise.
        * amd64-nbsd-tdep.c (amd64nbsd_init_abi): Likewise.
        * amd64-obsd-tdep.c (amd64obsd_init_abi): Likewise.
        * amd64-sol2-tdep.c (amd64_sol2_init_abi): Likewise.
        * amd64-fbsd-nat.c (amd64_fbsd_nat_target): Likewise.

The change to amd64-fbsd-nat.c was done "blind" (no access to system),
but is reasonably straightforward. The changes to the -tdep.c files
were verify by rebuilding GDB on x86_64-linux when configured with
--enable-targets=all.