coresight: add system instruction access to etm for AArch32

According to the ETMV4 spec. ETMV4 support two type of access
operations, memeory mapped access and system instruction access.
In some specified chipsets. The memory-mapped access may result
in secure watchdog bite accross power collapse.
Add system instruction access to ETMv4 for AArch32 to fix the
compiling errors.

Change-Id: I1ec69e70bf83359374700e579191fac755a3a64e
Signed-off-by: Xiaogang Cui <xiaogang@codeaurora.org>