linux-user/arm: Remove unused get_put_user macros

linux-user/arm: Remove unused get_put_user macros

In linux-user/arm/cpu_loop.c we define a full set of get/put
macros for both code and data (since the endianness handling
is different between the two). However the only one we actually
use is get_user_code_u32(). Remove the rest.

We leave a comment noting how data-side accesses should be handled
for big-endian, because that's a subtle point and we just removed the
macros that were effectively documenting it.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>