Align AARCH32 version of debug.S with AARCH64

Re-order code (put panic and report_exception at the end of the file).
Export asm_print_* functions.
Add asm_print_line_dec macro, and asm_print_newline func.
Align comments in both AARCH32 and AARCH64 files.
Add blank lines in AARCH64 files to align with AARCH32.

Change-Id: I8e299a27c1390f71f04e260cd4a0e59b2384eb19
Signed-off-by: Yann Gautier <yann.gautier@st.com>