debug: add more strict checking for show_regs [2/2]

debug: add more strict checking for show_regs [2/2]

PD#SWPL-7711

Problem:
Executing echo l > /proc/sysrq-trigger each 5 seconds for about
15 minius will trigger hardlockup

Solution:
Add more strict checking for show_regs to filter out addresses
in secure monitor region and ioremap region, deferencing which
triggers external abort on none-linefetch, and finally leading
to hardlockup

Verify:
Locally pass on U200

Change-Id: I6bd219e7dc3ad29904e6bd1b7d2f4cfb3928d8ed
Signed-off-by: Jiamin Ma <jiamin.ma@amlogic.com>