target/m68k: add index parameter to gen_load()/gen_store() and Co.

target/m68k: add index parameter to gen_load()/gen_store() and Co.

The instruction "moves" can select source and destination
address space (user or kernel). This patch modifies
all the load/store functions to be able to provide
the address space the caller wants to use instead
of using the current one. All the callers are modified
to provide the default address space to these functions.

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20180118193846.24953-5-laurent@vivier.eu>