linux-user: ppc64: set MSR_CM bit for BookE 2.06 MMU

64 bit user mode doesn't work for the e5500 core because the MSR_CM bit is
not set which enables the 64 bit mode for this MMU model. Memory addresses
are truncated to 32 bit, which results in "Invalid data memory access"
error messages. Fix it by setting the MSR_CM bit for this MMU model.

Signed-off-by: Michael Walle <michael@walle.cc>
Reviewed-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
