arm: show extra regs only for kernel mode

Align with 64-bit implementation, It is meaningless to show
extra regs for user mode. Also remove show around regs r0->r10.
It will cause some NOC errors if showed address is protected by TZ.

Change-Id: Ic1d2a985c690de21d46926e310f2b341d8264255
Signed-off-by: Zhenhua Huang <zhenhuah@codeaurora.org>