linux-user: Move CPU type name selection to a function

Instead of a sequence of "#if ... #endif" move the
selection to a function in linux-user/*/target_elf.h

We can't add them in linux-user/*/target_cpu.h
because we will need to include "elf.h" to
use ELF flags with eflags, and including
"elf.h" in "target_cpu.h" introduces some
conflicts in elfload.c

Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20180220173307.25125-2-laurent@vivier.eu>

linux-user/mips64/target_elf.h

@@ -0,0 +1,14 @@
+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation, or (at your option) any
+ * later version. See the COPYING file in the top-level directory.
+ */
+
+#ifndef MIPS64_TARGET_ELF_H
+#define MIPS64_TARGET_ELF_H
+static inline const char *cpu_get_model(uint32_t eflags)
+{
+    return "5KEf";
+}
+#endif