String instruction emulation would erroneously result in a segfault if
the upper bits of the EA are set and is so high that it fails access
check.  Truncate the EA to 32 bits if the process is 32-bit.
Signed-off-by: NJames Yang <James.Yang@freescale.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>