Fix build breakage in NetBSD tdep files

Fix build breakage in NetBSD tdep files

A recent patch caused some build failures in NetBSD tdep files.  I saw
this failure in my --enable-target=all build.

This patch fixes the problems.  Tested by rebuilding.
I am going to check this in.

gdb/ChangeLog
2020-04-06  Tom Tromey  <tromey@adacore.com>

	* sh-nbsd-tdep.c: Include nbsd-tdep.h.
	* ppc-nbsd-tdep.c: Include nbsd-tdep.h.
	* mips-nbsd-tdep.c (mipsnbsd_init_abi): Add missing ";".
	* arm-nbsd-tdep.c: Include nbsd-tdep.h.
	* hppa-nbsd-tdep.c: Include nbsd-tdep.h.