Cortex X3 erratum 2743088 is a Cat B erratum that applies to all
revisions <= r1p1 and is fixed in r1p2. The workaround is to add a DSB
instruction before the ISB of the powerdown code sequence specified in
the TRM.

SDEN documentation: https://developer.arm.com/documentation/2055130



Change-Id: I2c8577e3ca0781af8b1c3912e577d3bd77f92709
Signed-off-by: Harrison Mutai <harrison.mutai@arm.com>