linux-user: Split out cpu/target_proc.h

Move the various open_cpuinfo functions into new files.
Move the m68k open_hardware function as well.
All other guest architectures get a boilerplate empty file.

Tested-by: Helge Deller <deller@gmx.de>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
diff --git a/linux-user/mips/target_proc.h b/linux-user/mips/target_proc.h
new file mode 100644
index 0000000..43fe29c
--- /dev/null
+++ b/linux-user/mips/target_proc.h
@@ -0,0 +1 @@
+/* No target-specific /proc support */