linux-user/main.c (m68k): Use get_user_u16 rather than lduw in cpu_loop

linux-user/main.c (m68k): Use get_user_u16 rather than lduw in cpu_loop

In the m68k cpu_loop() use get_user_u16 to read the immediate for
the simcall rahter than lduw, to bring it into line with how other
archs do it and to remove another user of the ldl family of functions.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-id: 1421334118-3287-8-git-send-email-peter.maydell@linaro.org