hikey: mmio: add isb when load/store any register
hikey: mmio: add isb when load/store any register

After added isb command, this issue has gone.

Platform exception reporting:

ESR_EL3: 0000000002000000

ELR_EL3: 00000000f9803488

Platform exception reporting

Signed-off-by: Haojian Zhuang <979139d45d262f0480136b0da512e0afa0fe79d3@linaro.org>

vchong/arm-trusted-firmware,96boards/arm-trusted-firmware,vchong/arm-trusted-firmware,96boards/arm-trusted-firmware