feat(debug): add helpers for aborts on AARCH32

New helper functions are created to handle data & prefetch aborts
in AARCH32. They call platform functions, just like what
report_exception is doing.
As extended MSR/MRS instructions (to access lr_abt in monitor mode)
are only available if CPU (Armv7) has virtualization extension,
the functions branch to original report_exception handlers if this is
not the case.
Those new helpers are created mainly to distinguish data and prefetch
aborts, as they both share the same mode.
This adds 40 bytes of code.

Change-Id: I5dd31930344ad4e3a658f8a9d366a87a300aeb67
Signed-off-by: Yann Gautier <yann.gautier@st.com>